Nice try IO but unfortunately the CAA beat you to it. All non- G-reg homebuilt or experimentals are subject to the same rules - there is no different between N and EASA regs, written permission is needed to operate in the UK and I think a maximum period of 30 or 60 days.
Again it comes down to them presently being outside both the ICAO and EASA arrangements (as Annex II aircraft) subject to national rules.