Do we paint or not paint? If we don't paint, definitely wood fence posts, but if we do paint, what about concrete? And gravel boards?
If we paint, what colour?
Also, end of the garden, we have views over a park, so we are having a half height wall (probably rendered breeze block which will need to be painted) and shutter fencing above like this www.tuin.co.uk/Flex-Fence.html so we can take in the park view when we want but privacy from users when we want.
Wooden posts go rotten and break off. It is very hard to break up and dig out the concrete they have been set in when that happens, much more work than building the fence. Professionals will not even try, they will leave the old concrete in the ground and build a new fence with the posts along a bit. Metal spikes are rubbish.
I strongly recommend the concrete posts, and concrete gravel boards too, set slightly into the ground.
To make them blend in with the woodwork, if you are going to stain the panels dark brown, you can use dark brown masonry paint on the concrete, preferably painting before installation. I find light brown does not look convincing.
Fence stain is not paint, it is a water based waxy water repellent coating, and very easy and cheap to recoat after 5 years or so when it weathers. If one day you want to change the colour, it is easier to go from light to dark.
If you use a colour such as mauve or blue, you can blast it off with a jet washer when you change your mind.