G'day Shaun,
Been through this recently,
Kits for W1's are available from this bloke
http://www.classiccarbs.com.au/
Not sure how familiar you are with the W1 but heres a couple of things I learned after rebuilding one.
Be very patient with the brass slotted head fittings you'll have to remove to get into the circuits and ports. If you burr them (badly) they will prob never come off. In which case a lot of Carbie cleaner & compressed air will have to do.
The kits (off this guy) come with only the accelerator port brass fitting but it does have all the gaskets you will need and an accelerator pump.
Two suggestions...... hunt around for a siezed or broken W1 - and get out any of the brass fittings you can. Heat the carbie with an oxy then squirt the WD40 on the fittings - should free them up before you attack them with a screwdriver.
Might be telling you how to suck eggs - hope it goes smoothly