On Monday, 20 June 2011 11:37:30 UTC+1, richard wrote:
they hold the frames square in the metal frames.the units are about 12
years old.
Searched forum history and make many wasted phone calls.Hopefully
someone out there has a good link
Many thanks

Just to update this question.

I have Everest secondary glazing with the afore-mentioned plastic clips.
I couldn't find replacements anywhere on the internet.
Rang Everest [0800 140 4936]and they cost £5.00 postage for as many as you need, i asked for 40.
I read somewhere they are called Anti-crabbing clips.

Hope that helps anyone googling or searching for this.