I would suggest CT1 - http://www.ct1ltd.com/en/ct1.html - I use this stuff for loads of different jobs and it's great.
Odourless
Does not shrink
Can be painted
Contains no solvents
No isocyanates
Unique flexibility
Enviromentally friendly
Not many places stock this but i found some at my local covers.
CT1 is great stuff. You can buy it at Edmundsons electrical wholesalers