19 sounds good to me! I live with my inlaws, and they have the heating on ALL the time. The house is constantly between 26-29. It's really uncomfortable, and god knows how much they spend on heating! My FIL is always wearing 2 jumpers too, I think it's unhealthy!
After asking them to think about turning it down, and having them complain about the cold (!!), we turned our bedroom radiator off and keep the door closed, and we manage to keep it between 22-20, and Poppy wears a 2.5 tog sleeping back with a vest and baby grow.
Now all I have to do is find some way of keeping Poppy away from radiators when she's crawling in case she burns herself. :/ The funny thing is, my MIL came into our bedroom one night before I had Poppy, and we had the window wide open because we were boiling, and she said we'd have to keep the room much warmer for the baby, she was shocked when we said we had to turn the radiator off and told us to put it back on when she comes! I said there was no way, the monitor was already registering 26!