This is what I've got...
http://www.evasivemotorsports.com/mm5/m ... ValveStems
... So they're not standard. The two 14mm diameter seals are the important thing (Although I'm sure I could get away without the outer seal with the right valve).
The hole is about 11mm diameter and there's a 14mm recess each side (Which is what the 14mm seals sit in).
I could do with them soon as I'm having to pump up my tyre every two days, so hoping to find some in the UK and for a reasonable amount. I don't want to be waiting until the middle of next month for some from Hong Kong, but I also don't want a set for £3.96

Does anyone know of a decent website with some good options?