pseudonym wrote:
Don't bleed the pressure.
Pull the connection fitting and hose from the lid fitting end.
Aha!!! That seems to be the johnny!!!

Looks like it's the rapid decompression of yanking the hose off rather than the slightly slower valve release that causes the lid to shlump on! When removing the jar sealer I seem to be dislodging the silicon seal ring each time and have to put it back inside the sealer, dunno if that will shorten its life, but yaaaay!!!! It's working! I have sealed Kilner jars!

Happy bunny!! Thank you so much!!!! Now...must allow time for my right hand to recover....all that pumping and yanking is taking its toll!!!! (It's a gift...go on!!)
Brambles I am now in love again with my Foodsaver lid sealer! If you have someone in the US who can get one for you it's about $10, otherwise it's about £10 plus £12 postage from fleabay. It's about £40 on Amazon! I paid about 50p more because I picked a seller that did the whole Global Shipping Program which meant a) it was tracked every step of the way; b) it didn't get held up in customs. You can get both a regular-mouth and wide-mouth lid sealer for another £5. I didn't go with the wide-mouth sealer on account of the fact that I don't have, or expect to get, the Mason Ball wide mouth jars. I might give the Ball sealing discs a try, now I know they are the same size! Brake bleeders are about £15. It does require quite a bit of "grip" for the pumping hand (ooer missus), particularly on the litre jars so perhaps not for the arthritic of those with very small hands (I have small hands, I can barely grip the bleeder! - but perhaps a different bleeder would fit me better). Follow Pseudonym's instructions and all should be good!
Update: just bought a load of Ball Mason regular mouth lids from the US which end up cheaper, even including postage, than buying Kilner lids here! Now if only I could find cheap postage on an All American Canner....!