Serious question: where an overflow pipe was removed from the house, there's a small hole halfway up the wall. I've seen blue tits flying up to it and going in, but so far, I haven't seen one coming out. Do you experts know if a blue tit can turn round in such a confined space, or is there an ever-mounting heap of late, deceased, bereft of life blue tits inside the cavity wall? I 'd like to block the hole up to avoid this rather worrying possibility, but would hate to think I'd done so while there's one or two still inside.

If you wait till the summer you'll probably be safe to do it, but any bereft tits in your cavity (ooerr, missus!) will be difficult to remove. Good idea to block it up anyway, in case you get bees or wasps nesting in there.