@marioman: Vegemite is stocked by the larger supermarkets in the UK - fortunately; I used to like Marmite but nowadays I don't like its treacly consistency, so I buy Vegemite instead.
@ccf: I've only ever heard it called black pudding. I quite like it, but only occasionally. When I used to drive a van the better drivers' cafes used to serve it as part of a 'full English' breakfast.