Every now and then, key in ignition, turn on, I get radio etc but no dash lights and car won’t start.
It seems worse if the car is warm, new battery about 6 months ago, it just happened at home and
I tried a booster to see if low voltage was the cause but no still a dead dashboard.
10 mins later all is well and it started.
Any thoughts?

There are a lot of threads on this across the internet, and I recently suffered exactly this issue.

Cold starts fine, warm starts after about 40m driving while the car still warm were usually a fail, then after 20-30 presses of the button the car would fire up.

Over the months I had a new battery (didn't solve it) new starter (didn't solve it) before my main dealer agreed to take it back in and fix on their £££ as admitted they hadn't solved it.

After a few days of their top lead tech driving the car home and seeing the problem they traced it to high resistance in a main fuse in the car which was quite dirty, they cleaned it up and the problem hasn't re-occured in 2 months for me (so fingers crossed).

I'm no expert but believe the electrics on these cars are very complex and a bit flakey, so the issue may not always be the same when a similar starting problem is exhibiting itself.

See you aren't far from me in Epping - it was Bishops Stortford main dealer that got to the bottom of this for me.

Thanks I’ll look for that, any idea where it is?

nope sorry, no idea

but they were tracing thru the whole wiring loom looking for high resistance as suspected that was what was causing the start fails - says to me that the starting problems you can see discussed in many places are a variety of things, not a single fix.