We have a rather scruffy dormer bungalow and have planning permission for a small two storey rear ext and extra bedroom over what was an integral garage. This plus some internal rearranging of living space. Lots of bits of work but nothing huge.
Yet we've received a quote from the builder we were hoping to use of £300k including vat and all fittings. Good job I was sitting down for it. I'm sure we could knock the house down and start again for that!! This is in south east but not a massively expensive area.