The G36 youre looking at will be no use in airsoft, its underpowered at 225fps, and is likely to be inconsistent with accuracy and unreliable. As stated in its description its ideal for backyard shooting to get a feel for the game.
Perhaps you might want to hire a gun for your first few games and decide whether you want to incest in this hobby.
And as for a first gun, id recommend a G&G cm16 Raider which is a very good rifle for its price at around £130. Solid polymer construction with no wobble or creaking unlike other options within the same price range, ~350fps which is perfect for most airsoft sites in the UK and you wont be out matched, comes with a rail system which means you can add any attachments to your weapon in future.
There is a starter deal on airsoftzone which comes with the rifle, 450 round high capacity magazine, 1000 bb's, a 9.4V lipo battery and charger and a mask for only £159.99 which is a fantastic deal for beginners.