Thanks again, Stephanie, this time for the info re Levantina. A quick browse of the website makes me want to go and have a look.
When we Lived in North Yorkshire, I used to visit a timber importer not far from us. I'd spend five minutes in the shop buying whatever I wanted, then an hour wandering around the warehouse looking at timber imported from all over the world, and imagining what I could do with it. Levantina looks a bit like that to me.
cp - all the stonemason yards I've seen, and there are a lot of them, have been on trading estates or out of town centres. I don't know your area, but you could look at the following and see if they do Silestone:
Mármoles Pérez Y Berná , Joven Pura, 22 BAJO (URB NUEVA TORREVIEJA), Torrevieja
Otherwise try a kitchen specialist, especially if you want any design work doing. Also, if I search Leroy Merlin for Silestone, it produces quite a few results.