We have a Folk session once a month at The Monty Club in Eltham SE London. Guiness is £1.70 a pint That's an imperial pint (20 fluid ounces as opposed to a US pint which I believe is only 16 fluid ounces! - however in most of the local pubs it is about £2.40 a pint.

Personally I prefer to drink lager though.