I have to add my thanks too Phil. Always interesting to hear how other people do things. As others have mentioned, the house bricks are a simple but great tip. Wouldn't have thought they would hold moulds good enough but I believe you. Will save a lot of mucking around with the vice.
P.S. Mark, I use lead flashing occassionally in my business. Available from hardware stores or plumbing supliers, but it is bloody dear now. Don't know if the scrappies sell it, but I know they only pay about 30c/Kg for it. If you have to buy it new, yo may as well buy sinkers ready made.
Regards, Steve