Well was driving my XJ6 the other day and long story short loss brake pressure. I know its a brake line but being new to European cars as this was my first does anyone know if the threads for the brake lines are different.

 

OK.

They will be metric.

They will NOT be unique to Jaguar. OK, the length and some clipping tags or whatever will be Jaguar specific, but the actual ends will be a "standard" brake thread/pitch/profile.

The rears are a strange fitting at the caliper, banjo type from memory??, but so are Merc/BMW/etc, so again NOT Jaguar specific.

So if Jag hoses are not available (strange) any competent brake specialist will easily make new hoses for you.