Ordering airsoft within the uk??

Question

i`m thinking about ordering a jg g36c in twotoned green from www.airsoftworld.com. or maybe the m4 cqb. how ever they are both around 340 fps. i know theres a law on importing over powerd airsoft guns but is there a law on getting one from within the uk. i mean they check packages at HM customs but where can they check in the UK