On a number of occasions if I unlock the TD6 when I open the door I get about ten seconds of a relay chattering. I think it is behind the dash or in the centre console. No idea what it is or how to track it down given the intermittent nature of the issue.

Any ideas what I should be looking for?

Here you go Mike
https://www.fullfatrr.com/forum/topic56054.html

Awesome. Thanks.

If it's not the retaining clip, then it's the motor itself. I tried to fix mine by taking it apart but it only lasted for a few days at best. A new (used) motor cured the problem.
These are readily available on eBay and salvage yards.



And they're dirt cheap, too

According to Land Rover these motor units are no longer available to buy new.

The big question is, given that there are four of them down there, how to work out which is the problematic one without pulling the whole dash apart.

Or is it obvious once you have pulled the dash apart which one is the suspect one?

I took mine apart it's pretty simple I cleaned it greased it been as good as gold since.
There is x1 in the footwell then 1 or 2 behind the hevac panel both easy to get to.