I'm posting this because before I chose a product I did an internet search and didn't find anything useful.

I spent some time yesterday sealing around the interior of my PVC windows, only to find this morning that on many of them the sealer had cracked down the middle. I used Bostik MS Safe Seal. It's most likely due to poor technique, but I've rarely had this happen with Selleys No More Gaps products. I also used Selleys Exterior Weatherboards sealant yesterday outside, with significantly better though not perfect results.

So my opinion, in my old house that moves around a bit, is Selleys caulk over Bostik caulk for amateurs like myself. I know Bostik is a good brand, and maybe with better technique a professional can get good results.

I'm off to buy some Selleys Paint Over Sealant, which is like no more gaps bit a bit more flexible.