Dave Martin said the following on 22/09/2005 20:58:
I seem to remember a tip to use household spray 'silicon' polish to both
clean upvc plastic ( esp the woodgrain variety ) and to slightly
lubricate the usual sliding mechanism.

Does anyone agree ? .... Dave

Screwfix do some stuff he

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=11235

and:

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=26656