Pinnerite wrote:

Any clues about where to go to buy a replacement would be very welcome.
My location is NW London, near Watford.

But even if you find a replacement tile you will need to have it fitted.
I'd suggest contacting a decent local roofer is the thing to do. I know a
roofer in that area if that helps. Email me and I'll forward his contact
details.

--
Nige Danton - Replace the obvious with g.m.a.i.l