I've got a pair of old OEM Julies (on a recumbent, FWIW) – circa 2000-2002 iirc. Rear caliper's helpfully dumped it's load over the rear disk.
Now, to be fair I haven't tried Magura UK, but a) they're old b) well out of warranty c) 'not user servicable' according to the online guff (other than bleeding 'em of course).

Anyone had a similar scenario and managed to salvage them ? (Admittedly some other manufacturers don't do rebuild kits either…)

Curiously I've come across a few of 'em on ebay in a similar 'possibly bust' condition.

I suspect I'll wind up lobbing on some BB7s – I've got to split whatever I put on, and I can't be faffed with bleeding the damn things…