Please can someone tell me where to get this -

Supermarkets tend not to do this. Find yourself a good local butcher and he will do it for you. Alternatively look on this site and search for Paul Bloxam, Braised Salt Beef, it tells you how to salt the beef. It does work I have tried it - it is delicious.

If you do not feel like making your own (Paul's was lovely - tried it) You can most likely buy from a good Jewish Deli