Managed to get my plumber to come round this morning, as there has been some flapping from behind the gas fire, so it had to come out to remove the bird. Luckily, he is a friend of my sister's, so did us a favour coming today. He said it would be a pigeon (was correct), and he normally manages to grab them before they fly out (not this time), it got out and perched on the curtain rail. He managed to grab it from there, then was released out of the patio door. It seemed ok from its 2 or 3 day ordeal, and flew straight off. The plumber did ask if we wanted to keep it for tea though (wife would be horrified at that!). Cost 70 quid, but at least he serviced the fire (hoovered out and flue checked), so one less job to do!