Common misconception is that UKARA is a "licence" and you need one to own a RIF. UKARA is simply a database of registered skirmishers so that the person selling you the gun can quickly check you off a list to verify that you are, indeed, going to be using it for airsoft, rather than robbing the local corner shop. It's not a licence in any way - the seller can still refuse the sale even if you have UKARA if they don't believe you'll use it legally, or, on the contrary, a seller can sell you an RIF without UKARA - for example, I recently got into airsoft through filming - I was in an airsoft shop discussing options for prop guns and gear when I was working on a film project. Blank firers (for which you need to pay an armourer for a day since you're working with live ammunition and firearms), PFC guns (which aren't too reliable and often give out unrealistic sparks), or, what we went with in the end - airsoft pistols with black BBs so they didn't show up on camera, but still had the full working blowback action. We purchased the RIFs, I didn't have UKARA or such like, but I had a valid VCRA defence as "Film and Television".
The VCRA defence is applicable to the purchase of weapons, or the manufacture of them. You must have a defence to do either. You don't need UKARA to buy a RIF for airsoft either. As long as the seller is satisfied that it will in fact be used for airsofting (or other legal use), they can sell the RIF. Same goes for manufacturing. If you manufacture a RIF for airsofting, no problem. Of course, if the police came along, you may have to prove that. Which is why ukara is helpful.
End of the day, common sense is key. Are you spraying it black for use in an airsoft skirmish? Or are you just spraying it black to look cool? One is legal, one is not.
Funny side note - by legal definition, "film" in the VCRA act is, according to the patents and copyrights act directly referenced, “a recording on any medium from which a moving image may by any means be produced. So, you could technically buy a RIF, do a review video on it, and be on your merry way.
Or, just use a helmet cam when you skirmish. Then you've got 2 defences at the same time.