Bob Mannix wrote:

snip

One of my patio doors went in a similar manner (if it's any consolation), ie
with no cause. As it happened the poxy company who had installed it had put
the laminated sheet on the inside and the toughened one on the outside (the
wrong way round)...

Just a small point: how can you tell if they're the wwrong way round?
I've just had some windows installed in my loft conversion, and I can
tell the builders got the bathroom windows back to front (patterned and
textured bit on the outside), but how can I check that the clear-glass
windows are the right way around?

Regards
Paul