Peterb and lineaway,,
Thanks for the advice. Lineaway, u make it sound like it's fairly straightforward, an injection of confidence..
Then peterb, u give me a get out of jail free card with leaving the innards intact and just changing the tubes. This sounds really tempting, but it goes against my grain to disassemble them and not check all the innards - possibly never stripped down again..
So, I'm gonna combine your contributions, whack my tube into each yolk hole, then in the depths of winter strip them down and have a good look inside.
So yous have pretty much solved my quandary.
Turbofurball,, 'christmas is coming, the goose is getting flat..'
Cheers folks..