There is always this guy on eBay that do Jaguar repair panels, he'll be able to make up a will panel for you if needed.
Alternatively you could cut out middle section of a breaker, that's always fine, even on rust buckets.
1997, 4.0 LWB X300 - Unlucky car but still a daily driver.
1988, 3.6S XJS - Never ending restoration project.
1994, 3.2S X300 - Accident damaged, October 2015. Gone!
1994, 3.2S XJ40 - Long gone.