Cheers all.
Bought 2 of the ebay rolls and with delivery it came to £16.50.
Will let you know if I've shot myself in the foot when it arives!
Doubtless it will have 'many other uses around the home' though, if it's no good for the job in hand such as, erm, er, um...
Anyroad two more questions
1. Do you scrape all the foam sealer off first, before you apply the sticky rope stuff or do you just stick it on top?
2. Has anyone got the parts number for the plastic clip thingies that hold the door inner on (the ones that with every car I've had they snap the minute you try and take them off).
Cheers again folks