The major problem with UKARA and the whole proof of defense is it's badly thought out and spectacularly badly implemented. The only thing UKARA help's and serves is retailers so they can put a nice check mark next to a sale to proove they have asked if the sale is for airsofting purposes. In reality i can buy a two toned gun, remove the paint or easier replace the parts and if anyone questioned me which to be honest will never happen as no one really cares the answer would be i was given it. But in regards to proof of defense, site membership, UKARA alternatives, receipts from fields, pictures, video footage, signed diary are all perfectly fine for sale of RIF's, this misconception that UKARA is the be all and end all of defenses is perpetuated by retailers as it's easier for them for sale's. The whole situation needs completely overhauling and clear guideline's put in place. For example if i was a hardened criminal i could spray paint my real steel gun a stupid bright colour and now have an IF as most airsoft guns externally look identical to there real steel counterpart's, also could by a two toned plastic gun, remove the paint and use it to commit a crime. I'm exaggerating slightly but the points are valid, this whole spray painting helps and protects no one, absolutely no one as the poof of defense can be ignored if you so wish. Now i'm not sure how to resolve the whole issue but at present it doesn't work, the reason people argue for it is because they are law abiding citizens and so follow the rules and they would still do it if no defense was required as you already know that using your RIF for anything else but airsoft is wrong and so you wouldn't do it, everybody else really doesn't care.
I'm sure i'll be disagreed with, that's of course your opinion which i respect, that's my take on the whole situation.
As a final note which i just thought of, I would be curious to see the crime statistics that involved airsoft gun's before and after the inception of UKARA or proof of defence and see what effect if any it has had.