The Grand Opera House is a lovely venue in York which shows a wide range of shows. It is called the opera house yet it does show other things such as comedy stand-up and musicals. I've been a few times-last time was to see Jimmy Carr live which was great. There's a bar when you first go in which is nice for before shoes and the interval break.
The seats are comfy enough in the actual theatre and although there is not a lot of leg room this seems to be pretty standard for theatres anyway. There's a carpark nearby although you do have to pay for that.