Steve Firth wrote:

It depends how much you want to pay. Sikaflex is much better than
silicone sealant for use when continuously immersed. It's also much more
expensive. If you want a compromise then MS-polymer sealants (modified
silicon co-polymer sealants) are extremely good for use when wet. They
are slightly less jelly-like than silicone and can be sanded and
overpainted (not relevant in your application).

Evostick Nail and Seal is an MS-polymer sealant. You can get it from
some branches of B&Q mainly the larger ones. Don't get confused by other
products with similar names.

http://www.amazon.co.uk/Evo-Stik-Nai.../dp/B0001P03SS
http://www.tool-up.co.uk/shop/diy/EVONAS.html

This is the cheapest supplier I could find:

http://www.pvrdirect.co.uk/productin...?catref=EVONAS

Steve, thanks a lot! So helpful. I reckon for just a few pounds extra
it's worth me going for the Sikaflex. I don't want ANY water dribbling
in at some point in the future and have to go through the misery of
taking the ironware to bits again!

Eddy.