I don't really care if your dad has UKARA or not really I fail to see what you are trying to do other than say "the government don't know what they are doing and have stupid laws".
Yes your friend who is in the army can't buy a RIF even though he has permission from the government to bear arms for the protection of the country, but then neither can my uncle who has 6 privately owned firearms, or my friend who is a training officer with Hampshire constabulary Armed Units, they are all responsible people who have been trusted by the government to use or own a real forearm but that means sweet Fanny Adams when it come to the law surrounding RIF's and their ownership.
The law is probably never going to change and I am not fussed about that, so what if kids can't play as much arisoft, they aren't the ones who spend vast amouts of money on the hobby, the 18-45 year olds do as they are the ones with an income. I have no problem with kids playing airsoft if they can show they are mature and sensible enough to join in properly but alot of the time they aren't, they run around either breaking rules or not taking hits and generally pissing people off, my site runs a members only over 18's day about ones ever 6 weeks and guess how many incidents of cheating there are at those? 0 to date in 2 years, where as there are some walk on days that they chuck 5 people off the site due to rule breaking, and at least half of them are 14-17.
At no point will the government of this country deem an under 18 responsible for anything dangerous, even smoking is 18 now and I have heard rumours that driving is heading that way too.