Here's a list of a couple of guns from wolf armouies it's a pretty good shop it's where I've brought all my gear from.
G&P enforcer- http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=GP744
SRC m4 SR4 SD- http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=GE0509TMII
SRC m4 SR4 - http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=GE0512TMI
Dytac invader - http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=DYAEG07BK
G&P m4 sentry - http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=GP901M
They also do packages where you get 2 battery's, a mag, silicone and a chargerfor £99 http://www.wolfarmouries.co.uk/airsoft/bb/product.asp?page=product&id=98XPSBAEG
I have the G&P enforcer which is the top link I put and it is a amazing gun it comes with a red dot sight and a vertical grip it shoots really fast and is a solid gun with with no wobble at all. I spend about £430 and got the gun a extra mag and then the battery package. You might want to spend a little more then £400 as you need a mask and a tactical vest if you want one
I have this vest and it's pretty good- http://www.amazon.co.uk/USMC-Tactical-Assault-Airsoft-Olive/dp/B0041300WK/ref=sr_1_2?ie=UTF8&qid=1425213722&sr=8-2&keywords=Airsoft+vest