When I was looking it seems like there are ways to insulate from above while the roof is off and insulate over the rafters. One of the roofers we had round was talking about doing that with TLX Gold but it was pricey and we needed to pull the conversion to pieces anyway and fix all the other problems.
Ta. I'm rapidly trying to skill myself up on this. If we are going to get the roof renovated I don't want to miss the opportunity to put other efficiency / comfort savings in.
When I was looking it seems like there are ways to insulate from above while the roof is off and insulate over the rafters. One of the roofers we had round was talking about doing that with TLX Gold but it was pricey and we needed to pull the conversion to pieces anyway and fix all the other problems.