I think the Odeon cinemas as a chain might be quite open to providing mum and baby sessions.
I went round and saw the manager of ours and he agreed pretty readily to trying it out. He said he'd been thinking about it and named a couple of other ones that were starting it up soon. We talked through what he'd need - baby changing, bugy parking etc and he's just got on and sorted it. The first sessions start next month.
Thought I'd mention it just in case someone else might fancy leaning on their Odeon to provide this service.