Maybe the rest of the world already knows this but I would like to draw your attention to the changes to cooper side mould now available.

Standard minis were fitted with a U-shaped plastic chrome moulding; Cooper Ss had a fancier, wider, contoured moulding, which was available as "genuine" and a "non-genuine" versions (GZF105).

The "genuine" version seems to have been discontinued. Mini Spares website says this is due to a ban on the manufacturing process of putting chrome foil onto plastic.
So the only choice now seems to be the "non-original" moulding. I assume it isn't made in the same way as the banned version.

But the "non-original" sample I ordered from a parts outlet was a very flimsy material that folded and creased permanently when it was opened out and straightened. The genuine moulding was a lot tougher although still a battle to fit neatly.

I have scrapped 2 lengths of the "non-original" already but if that is the only thing available, I'm going to need a better method of fitting them.