We asked a local surveyor to come and look and he said it was to do with the fact that one particular wall in the bathroom wasn't well supported as the joist ran the wrong way underfloor (the bathroom is a triangular shape - cut out from another room at some stage in the house's life). He told us to move the heavy furniture away from the wall on the other side (in my daughter's room) - which we did, but the cracks have got worse.
On top of all this cracks have now appeared all the way up the stairs where the wood skirt is now coming away from the wall, the dado rails are moving slightly too. The ceiling downstairs is showing lots of new cracks....I could go on and on....and I thought it was all to do (initially) with settlement of the extension. The whole bloomin' house seems to be on the move.
We want to redecorate our daughter's room but I'm loathed to start because it's bound to crack again as soon as we have decorated.