[billjam]

Update ...
After a night's soaking in WD-40 and then some Naval Jelly (that's with an "a") and then some prodding with bits of wire from both sides, the little stuck bits in the squirters unstuck themselves.
After copious flushing with various cleaners and petrol (some call it gas!), they are now all working fine.
Fleiger and I would still love to see what's inside one of these squirters if anyone is in a position to post a photo.
Bill