Here -
http://www.base-camp.co.uk/ - is probably the bast source for spare parts in the UK. They also have exploded diagrams of the stoves, with part numbers etc.
These stoves were the Rolls-Royce of camping stoves in the old days - every self-respecting biker had one with them on bike rallies. Fuelled by draining a bit from the bike tanks - yes, petrol! - and they just kept ticking. (and BMW riders used to put them under their bike sumps to thin the oil sufficiently to get their bikes to start in cold weather...)
Nowadays its probably better to use Coleman fuel, or Aspen 4 or panel wipe, as it contains fewer additives and therefore less likely to gum up the works. The 8 - without the self-cleaning needle of the 8R - is probably a bit better at avoiding this "gumming-up", and some even claim it burns better without the self-cleaning gubbins. Can't say as I've noticed much difference myself though. More pronounced on the Optimus 123/123R.