… and way beyond. 
People already start suggesting flute makers who don’t even make poly flutes, and / or flutes that can by no means be considered within the OP’s price range.
@seonag: If it’s the M&E that took your fancy in the first place, I’d say go for it! There will always be other options to consider.
[crawling up out of the dark to voice an opinion]
Here’s what I did. When I started out, I couldn’t afford much, AND I wasn’t sure that I REALLY wanted to pursue the disease… err… instrument. 
So I bought a D flute from Doug Tipple. PVC, well made, a little long in the stretch, but you’ll need to adjust to that if you’re moving from boehm flutes anyway. Then after I played that for a year or so, I ordered a keyless flute from Terry McGee. Lovely man, fantastic flutes. While I was waiting on that to be made, I bought a mopane Casey Burns folk flute second hand off of a chiffer here. Also a great flute, and definitely worth the money. Nowadays, I play an antique William Hall & Son cocus that was resurrected by Jon Cornia. Couldn’t be happier. Over the years I’ve played a couple of delrin flutes, and the ones I played were fine. I guess what I’m really after is that NONE of the flutes I have owned were particularly expensive. The most I paid for one was the one from Terry, and it was one of his less expensive models. Keys? Yes, the Hall flute has them, and I love them, but honestly, I don’t use them much. As was mentioned before most Irish tunes can be played without keys, and most keyless flutes will crossfinger just fine with the notable exception of Eb, which Just Won’t Work for me, regardless of the flute.
We all have some kind of climatic issues with our flutes if we play wood. If you go with Delrin, then you can laugh at the rest of us. However, for me, playing a wooden flute is worth the occasional irritation of a tight or loose tenon. Keep them oiled and you shouldn’t have any problems.
Welcome to the ITM world. Find yourself a flute and go after it. An interesting thing that I’ve observed is that after all the bragging is done over this maker or that maker, we all tend to sound pretty much like ourselves regardless of which maker’s flute we’re playing, once we’ve warmed up to the flute in question.
[/opinion voiced. crawling back into the dark where I belong]
Well said Dow.
Well… it turns out that I’ve decided to go with the M&E flute after all.
I think it seems like the lowest maintenance option that still sounds decent - the clincher was that it has no cork or thread in the joints (just polymer) and I think for a total beginner, that seems less threatening than anything requiring care.
I feel stretched for time at the moment, so easy and stress-free means I’m more likely to use it.
I really just want something that I can get quickly, and that I can leave on the desk to pick up and play whenever I feel like, without worrying about maintenance to speak of (or whether the kids will damage it, etc). The M&E sounds like a good option from those points of view.
Once I have a clear idea of whether I like the flute and what features I want, I’ll start saving for a better flute (possibly with keys, possibly timber - the options seem to be endless, but hopefully I’ll have more idea of what I’m looking for by then).
I think half the battle was making any kind of decision (it was starting to look like I was going to order nothing just because of indecision 
), so now I’m ready to order it I’m hugely excited!! 
Thanks again so much for all the advice - it was very much appreciated! (And wish me luck!)
I think you will be happy.
I came from 15 years on the Bohem flute as well. I ended up buying a blackwood flute from Tony Millyard but I did play an M&E before I decided on it. The M&E is a really great flue and I would have kept it if it was made of wood. I just like the thought of wood, im not against delrin.
One thing I will stress to you is you really have to blow different into an Irish flute. I knew this going in but didn’t fully implement it, so I was getting frustrated. You have to blow more downward. For me it involved dropping the flute a bit to the cleft in my chin. Just giving you a heads up so you don’t get frustrated like I did.
Enjoy
Thanks Caspermilktoast, I didn’t know that… I’ll have to experiment a bit.
The M&E arrived a day or two ago and I’m really happy with it as a starting instrument. I had a good strong sound from it straight away, and can play some tunes, although it’s taking quite a bit to adjust to covering all the holes properly, etc.
It’s a lot of fun, I think I’m going to love the Irish flute.
Excellent! Welcome to the archaic dark side of the flute world!
Congratulations, I´m absolutly in love with my polimer keyless M&E.
Is a great instrument, not hard to play and with high volume and perfect tone. And the best, it is cheap
Enjoy it.
Not the whole story when you need to keep them adequately hydrated as well and neither oiling nor hydration in isolation is likely to give your flute everything it needs. Oil to protect the bore surface (and outside too if you like), but hydrate to keep the wood at stable dimensions…
I’ll give a plug for a Casey Burns Folk Flute. It is a wood flute, but if you take care of it as directed, you should be fine. I live in a hot dry and alternatively cold and dry climate too with no problems other than those of my own making. Granted you can’t put it in the dishwasher to clean it, and I do oil it regularly but do nothing to keep it at other than the local humidity. Overall it is a remarkable flute for any level of player - a very forgiving embouchure, and a warm lovely tone that carries well, even in a session.
I also have an unkeyed Delrin flute by Rob Forbes that is quite nice. Lots of volume and punch for sessions and quite indestructible. The embouchure is perhaps less forgiving than that on the Burns folk flute, it took me a little time to dial into, but after a few months the flute really shined. I get compliments at sessions on how it sounds.
As far as keys - it you have them you will probably appreciate them. Certainly not a necessity for most tunes you will encounter, with notable exceptions.
I’v played a Dave Copley blackwood for manny years, which is very easy to play.
I tried out a Gary Somers delrin Pratten at a session today.
I was amazed how easy this flutes plays, volume is no issue either, no bother, effortless!! 
I own a Somers Pratten flute with delrin slide. It’s a lovely instrument with loud lively voice which doesn’t cost much. And it’s made out of delrin… great for traveling and playing outside in any weather )
Well, the “adequately hydrated” part I took as a given. I find that If I’m playing regularly, then the flute stays pretty well hydrated. Otherwise, I keep a guardfather in the case. Regular playing (that’s daily, not weekly or monthly) goes a long way toward keeping the hydration where it needs to be. Helps with your skills, too.