[PaulRhB]

Wills is excellent, For future reference Slaters Plasticard also do A4 sheets in 2, 4, & 7mm scale. I cut it up into smaller sheets and glue it on which is especially useful for distressed buildings.
Two pics off our club layout using 4mm scale Slaters sheets.

 

[PaulRhB]

Certainly

http://www.slatersplastikard.com/Plastikar...plastikard1.htm

Page 2
0436 4 mm Scale Corrugations White .015" thick

Also available from loads of shops that stock slaters in the magazines.