What can I do with left over roast beef???

[cardy]

it seems ashame to waste it

Curry!

that's a good idea. How long would I have to cook it for to made the beef tender (well not chewy!)?

I slice the whole lot, freeze and then reheat however many slices you want in some stock / gravy voila roast dinner again without having to roast the whole joint - also more tender when reheated this way.