Dianavan, only thing i can suggest is to wrap the tank in a glass fibre jacket. maybe try fibre glass and resin, apart from that, i couldnt think of anything else...
Bobert, just to be on the safe side, when you have finished why dont you get an air test done by a local independent air analysis company, , at least that way, no one can sue the ass off you if they ever get asbestosis, but dont tell them you have touched it, tell them you are thinking of having it removed and want to know how intrusive it is in the air.
It´ll cost you a few quid, but at least you´ll be covered.