'Frame Sealant'?

http://www.screwfix.com/app/sfd/cat/...06370&id=14287
http://www.toolstation.com/search.ht...earchstr=26507

The latter being only 83p inc. free delivery.

Mathew

Matthew's advice is absolutely right in your situation, but the
problem illustrates what is wrong with moddern materials. The UPVC
windows were sealed with a material that probably proudly announced a
10 year guarantee. And then failed after a mere 25 years. If the
windows had been made of oak and the gap sealed with a paste made of
boiled linseed oil and fine sand the system could be expected to last
for ten times as long. Or more.