Not all warehouse events in the UK have a correct license (the only reason they are more common in London is its a big city and cops are busy dealing with much worse crime) so the full details might not appear until the last moment, it is now dangerous to publish too much info here as all UK sites are strongly monitored by cops and other security agencies and there is more enforcement against unlicensed events (10 years ago although the sites were still monitored the cops didn’t bother checking much of the info they gathered!)
However, the bigger psytrance parties are often advertised on facebook, and sometimes some info is posted here. It does seem that in some cases that the more pragmatic European approach is being adopted where it is possible to legitimately rent a warehouse and hold a music event in it for up to 500 people without having to spend more than about €30 on the actual license.
If your friends are British then they may already have the partylines or other more underground info. Though TBH if I were in BE and looking for a good event I’d go to NL rather than UK these days (its closer for one thing and there seem to be slightly less border controls, though I have read they still happen now and then)
