Hi Sally,
Currently between £180-250/day depending on experience and the job in hand.
Creative Partnership rates (Arts Council England) is generally set between 200-250/day in London and the South East, as far as I am aware. Artists, as anyone else, should also be paid for planning and meeting time.
Artist newsletter has carried out independent research and is a good source of information:
http://www.a-n.co.uk/knowledge_bank/topic/193936
best wishes,
Lilli