On 23 May, 15:21, (Steve Firth) wrote:
light comes on

So you don't want to reduce the thickness of the glass by 1mm, you simply want to cut the glass so that it fits inside the opening?

[ ... (snip) ]

Or am I misunderstanding you again?

A-ha! No, you're correct. That's all I want to do. The glass is
10.8mm thick, and that's perfect - just what I need. The problem is
that the height of the glass (848mm) is fractionally too tall. If I
could reduce this height dimension to 847mm, it would then fit snugly
inside the inner window recess area.

Problem solved perhaps? I'll ring the glazing shop tomorrow morning,
and report back with their answer+price.
Thanks.