There's actually the G&G 30th Anniversary Edition rifles at Zero One and also Land Warrior Airsoft I believe.
They're £150 each but that's not that much more than the cheapest standard Combat Machine CM16 (£100-£120) I think the Combat Machine range goes up to about £200, which are followed by the Intermediate line then Top Tech guns.
The thing about this 30th Anniversary Ed is that it also has a metal receiver. So I think it's especially good value for money.
In terms of performance and quality they are probably the best you can get for the price, which explains why we are always recommending them
You do need to buy a battery and charger with them as well, probably another £20 up to £50 max, for good ones.
I agree metal is overrated, in terms of sturdiness and build plastic guns are absolutely fine (unless you're looking at cheap shite under £100 AEGs) G&Gs for example are nylon fibre reinforced polymer, no creaky stuff. I'm not sure about G&G metal construction but I'd imagine it's okay.
Heard a story once a guy dropped one of his guns (dunno of the brand) out of his loft IIRC and the metal receiver actually snapped :0