Hmm, I had the saame on a few of our windows... B&Q had some rolls [draft exclusion type] which i stuck around the window to seal it on top of the seal that was there but had obviously failed, not sure what the roll/tape was called, but if you ask one of the guys in there, they will know what you need, they had different kinds too. Foam/Plastic, depends what you think and easy to stick on... Hope that helps, i'm looking for answers on my own probs and came across yours!
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