Warning - Don't use U-Pol Grey Strip Seam Sealer
 

It would appear that it behaves like a paint stripper with certain paints, It's highly volatile but there are no warnings or significant directions on the tin. I'll be staying away from it and other U-Pol products in the future. www.rust.co.uk are supplying me with some small tins of paint to redo the damaged areas. Can't recommend their product Mastic 121 Paint, and service enough. It was news to them that U-Pol's product could do this, even with fully cured paint.

Think its got thinners/solvent in it so possibly will attack plastic etc.

Depends on the paints base. Cellulose based paint reacts with xylene based paint, and vice versa. Also, xylene is used to strip powder coating (turns it into a rubbery mat). Cellulose paint is ok with powder coating.

It just doesn't say anything on the tin and they sell it in halfords! FFS!