Wow, two people saying things that aren't replies to my dumb questions, I feel like I've arrived! 
I'm not sure about recipes for toffee vodka as I think I would just drink it! I imagine it'd make good cream-based cocktails though.
mog - sure, but it was a bit made up as I went along from 3 recipes none of which I wanted to follow exactly. But here goes:
800g plums
300g sugar
200 ml cider vinegar (I imagine any vinegar would work given what you do to it though)
About 20 black peppercorns
3 sticks cinnamon
3 bay leaves
2 stars of star anise
Sterilize your jars.
Halve the plums and take the stones out. Put them in a wide saucepan (it took two layers of mine.
Put the sugar and vinegar and spices together in a different pan. Bring to the boil, then simmer for 5 mins or so. Pour over the plums in their pan, and set the plum pan back on the heat. Bring to the boil and simmer for a couple of minutes.
Leave to steep for an hour or so then scoop the plum halves and spices out of the liquid (there'll be loads more as the juice comes out of the plums, and the plums will be a bit mushy but not totally shapeless). Discard the bay leaves.
Reduce the liquid by boiling hard for 15 mins or so.
Put the plums in jars, pour over the hot liquid, and seal.
I tasted them and they're nice - I'm going to buy a gammon joint for next sunday and try some as I had more than would go in my jars, but I like them. Hope you do. I tasted the liquid when it was cool to see if it was right for me, but I don't have much of a sweet tooth and you might want more sugar - you could add it before you boiled the liquid down, obviously.