Tony Bryer wrote in
:

I may opt for upvc or timber, depending on cost.

Timber is more expensive than pvc, especially once you add on the
units, which are included in the pvc price

A third option, though you'd have to look a little harder to find a
fabricator, is thermal break powder coat aluminium. Near maintenance
free like plastic, and much slimmer like timber. More expensive
admittedly.

Thanks.. That's good to know, as my windows are smaller than I'd
like,regarding the amount of light they let in.

Al