Decorator's Caulk

I've always had good results with Vallance caulk - which beats anything the sheds sell.

S/F do it in 2 sizes - the larger of which requires a full length sealant gun - some of the commonly available ones ain't long enough. [If it's long enough for Gripfill, it'll be ok]

I used loads of Evo Stik All Purpose sealant last year, especially the translucent version because you can see when it's fully dry. I prefer it to silicone sealant because it's overpaintable. Claims to be 30% "stronger than" silicone, whatever that means. Little shrinkage. Not cheap. Unfortunately Screwfix have stopped doing both white and clear versions as far as I can see.

B&Q translucent acrylic sealant is OK but shrinks more.

In article , Roger Mills writes

Agreed. my local independent DIY store does it very cheaply too. Beats the arse off mixing Polyfilla.