hi jill,
for coloured signblanks try glasplas
http://www.glasplas.co.uk
they produce some nice finished fiberglass moulded sign blanks.
and ashby trade sign systems
Tel : 0118 981 5343
Fax : 0118 981 5335
Their speciality is aluminium post and plate systems.
For a job we did about 1 1/2 years ago, the fella wanted board fixing to his corrugated cladding. He wouldn’t pay for an ally. frame (which is probably the best way) so I just used some 1.5″ self tapping screws and covered them with white screw caps.
For ally. frames try SignMakersProducts
http://www.signmakersproducts.co.uk
Hope this helps
ANDY
P.S. Did you get my fax??