I’m having the same problem as you- wanting the full auto feature. I think they’re still available on some American sites- which you may be able to get imported (not entirely sure), which you would have to supply your UKARA with when ordering probably. However, I’ve heard from a few videos that the full auto feature damages the gun’s intervals, which is why they stopped it in the UK.
Ive found a site which do it from Northen Ireland, if your still interested- bullseye country sport.