Rejuvenating UPVc seals


I have PVC windows about 15 years old. The windows and glass are good (no warping), but the seals are not working properly. Is there any way I can rejuvenate the seals, to get them a little more flexible again?
The seals look to be black rubber of some sort, V-shaped, with a little T-protrusion hanging off one side that slips into a groove on the window frame (kind of like this: V+). The seals have basially closed up through being closed over the years. Can they be softened so that they open up again? Is there anywhere to buy new seals from (I've looked everywhere - no-one seems able or willing to supply a consumer).
In the meantime, the winter wind howls through the gaps around these windows. The gap that needs sealing is about 6mm (same seals used inside and outside), and the V-shaped seals have closed to about 5mm. I can't see anywhere to stick on any additional seals.
-- JJ
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snipped-for-privacy@acadweb.co.uk says...

I went to the local DG firm and slipped 'em a tenner for a roll of the rubber and just replaced 'em.
--
Roland Butter :- There\'s nothing like a knob of butter.

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