Hi Pete,
I have a £20 diagnostic tool which I have used to get rid of the odd code or two concerning the EGR valves on my s type.
When I have had a park brake warning I have disconnected the battery, paused for 10 minutes and then connected the battery again, shut up the warning alarm, and then pressed down footbrake and handbrake at the same time, switched on the radio [you need the code ] and then reset windows and sound. I had also removed the warning light.
A nuisance but it has saved me a few shillings.
Regards,
Peter.