Nice to see you back on the forum Andy
If budget isn't a problem Hi-Spec have some nice kits for disc sizes that will fit inside 15" rims. I think they even have a 6 piston caliper that will fit. They used to list a Jaguar kit but they have taken it off their web page.
It might be worth droping them an email and asking what they can supply. Here's a link to their web page.
Hi-Spec
Cheers