How to get a photopass for gigs? (UK Venues)?

Be very nice to the PR office for the venue, or the Band's manager, then hope. Otherwise it's a matter of sitting tight, and working your way up the food chain, rather than approaching local bands almost as a cold call, actually get to know the band members, become friends and then work from the inside. This way you don't just build a portfolio, but your building bridges and reputation. It may be only in the local area but that's where it all starts.