aye, well, to put a bar into. not a diy job then? (bare in mind that i have the diy skills of a paraplegic in a straight jacket).
My mate had a sound job done ..converted into new living room. Pumps, sealing & all...not cheap though Will ask him who did it if you are interested
Try and get hold of a copy of the book "The Sunday Telegraph book of house & home building, maintenance and renovation" by Jeff Howell. It has a good guide to converting cellars and I think, doesn't recommend tanking-out but some sort of breathable membrane that you can plaster over. You could try emailing the author of the book as well for advice http://www.ask-jeff.co.uk/