Worth looking on ebay for rtv silicon.You can get some good deals from time to time. Hobby craft also sell it but its about £20 a tube.Good quality but dear.
I've used this stuff for molds and its been fine,
http://www.ebay.co.uk/itm/RTV-Silic...725029?hash=item4191119da5:g:X2kAAOxytL9SKw7E
Also used this, really good product but as I said its dear,
http://www.hobbycraft.co.uk/trylon-silicone-rubber-250-gram/573572-1000
Hope that helps.....
I've used this stuff for molds and its been fine,
http://www.ebay.co.uk/itm/RTV-Silic...725029?hash=item4191119da5:g:X2kAAOxytL9SKw7E
Also used this, really good product but as I said its dear,
http://www.hobbycraft.co.uk/trylon-silicone-rubber-250-gram/573572-1000
Hope that helps.....