I do sessions in Sheffield at various venues. As has been posted the lead or anchor muso in most of the Sheff sesh's gets an amount of dosh starting at around £20 upwards. One pub I play at pays me in beer (bad move I hear people who know me say) and taxi home , landlord there has been known to bring a tray of drinks round but always provides sandwiches for everyone. I think most pubs should pay but it depends on whether you've asked to play there or been approached by a landlord.