I am assuming the following things:
1: you are under 18
2: you do not have a valid skirmish defence, ie UKARA
so you are looking at a two tone weapon for £130
Now not knowing if you want to snipe or shoot then I can offer the following advice. DO NOT SNIPE TO START WITH, it is not like a PC game or real life sniping, there is no 1 mile kills. Sniper rifles have 1 shot and can shoot a LITLE bit further than a well set up assault rifle.
So based upon those sage words of sdvice to a starter, and also having no idea as to what type of site you will be playing at, be it woodland or close quarters, I would recomend the following
ics m4 transparent
g&g m4 or ak47 two tone
both are around 300-320 fps, so within both site limits, both are two tone, both can be bought in the UK
however a bit more info would be appreciated for help (also try to se the search function or scroll down a bit as it is asked over and over again)