Hi Bling

Also in the UK and I have defo seen aquarium sealant for sale at my LFS. One of the LFS that deals in marine fish has several items for "rock out crop" construction, so I would defo have a nose in the LFS for a product maybe more suitable than sealant!

Sorry I dunno any brands in particular on the construction side, but I have been looking at Dow Corning Silicone Sealer that retails for about £2 for a small tube, alot cheaper than the Juwel sealants that some shops stock.