£18k for a 52k mile 4.4 is in the present market but it's not a question of budget - Just not going willing to sit in a possibly busy train carriage for 1/2 a day to get there.
Take your points on the facelift 3.6's though esp the re the brakes.

I test drove a 3.6 and the 4.4

I bought the 50th 4.4 I viewed.

What was wrong with the first 49 you saw……
So as a result of useful comments here and the scarcity of actual low mile 3.6 models I’ll confine my search to 4.4’s.