Hi Kev,
for manx covers bands you can't go wrong with Brazen.
For originals Gratiz3 (us ) will be playing:
Mad Sunday in the cornerhouse
June 8th Having our cd launch in the cornerhouse.

also check out
Uber-Room
On A Friday
CircusWorld
Maldune

http://www.manxbands.co.uk have a gig guide which should be able to sort you out. but don't forget.

http://www.gratiz3.com *shameless plugging finished*