True about the Castle – we finished it last Friday after having had enough of the landlord's rather unpleasant attitude. We're looking for somewhere else to play in the town on Friday nights, as it would be a real shame to loose the only town centre Irish session.
The Harrington Arms in Gawsworth is well worth a visit on Fridays, with a mixture of English, Irish and some bluegrass stuff chucked in. The ale is great and the pub itself is arguably the best in England (ooo! that'll stir it up! :) ) in my 'umble opinion .
I think Pete Blackthornes' Puss in Boots session is on the first Tuesday of every month. The Farmers Arms Irish session in Wilmslow happens every third thursday (I think).
Further afield, if you're about on Sunday try the Whistling Jig in Stockport for some fine Irish music, though you can get 20+ players up there so it's an ensemble performance, but the quality's good and you may get to see Mike McGoldrick if you're lucky.