Thanks folks
Tom Ill give that a try, Ill have lots of sand coming out of the old tank, so thatll be handy anyway.
Ive mended the tank now, with a nice peice of new glass. Siliconed in easy, amazed how easy it was to do. The hard part was cleaning up the old crappy silicon around the old bit of glass.
It might take me a while to set this new one up, as Ill need to buy new PC tubes and a longer outlet hose, but should be good

very much looking forward to it.