Hello Baz,
Bedford brakes are starting to become harder to get hold of. I needed one cylinder for the mw last year and the cheapest i could find was £100 for an original O type cylinder. In the end i had mine re-honed and resealed and luckily it took and i haven't had any leaks so far, finger crossed.
The j type Bedford wheel cylinder is the same apart from the bleed nipple is a different size to the banjo fitting, so they are handed, where as the o type can go on either side. The easiest way round it is to drill and tap the smaller hole to the bigger size and then you have a straight replacement. Or if you fitting a pair i don't think anyone would notice the nipple size. Bernie smith has some j type cylinders at £70 each last time i asked. If you want his number PM me, he's usually at stoneliegh. And the chap that re-honed mine has the J type ones , at £70 also, so i could pass his number on too, if you like.:-D
When i was looking for one john morter had some o type ones again at £125, but he wanted the old one back so he could have it re-sleeved. I did look into having my own done and i think i was near £100 to have them done, but I've heard some bad things about the re-sleeving since.