I’m no expert but if you want a nice clean finish it’s best to get a plasterer to skim the walls. You could try some filler like Polyfiller in the dips, let it dry hard then gently sand smooth.

Lovely garden. I had a little garden a while back that had white painted walls and lightish grey painted fence with natural decking. The grey made the fence recess and the garden feel bigger and the white reflected light and made it feel bigger too. The planting looked amazing against both because the greens really pop against the homogenised background. So I think you should paint it too, but personally I'd find a complementary grey. Cream and grey are great together.

I think the walls will look super. I would also paint the radiator to match. I would probably paint the ceiling a pale grey to help the white coving stand out. And personally I would choose a more neutral bed because it’s inexpensive to change a wall color or bedding if you later fancy a change- but a bright colored upholstered bed is going to tie you in to certain looks only

I have used lots of paints and had a chat with the people at the Brewers near us recently as I'm helping a relative choose colours for a Georgian house overhaul. My own opinion on Paint and Paper library was already that the quality was amazing but the guy at Brewers confirmed it. He also confirmed that (sorry) but F&B is generally awful, watery thin and poor quality. Paint and Paper is easliy at the top of the pile when it comes to quality, Little Greene a possible second. I was tyring to find a really good neutral for my Auntie's House and Stone came out tops, not too yellow, not too green, a perfect neutral. The Stone 1 or 2 was good for woodwork the Stone 3 perfect for walls. I can't comment on the suitablitity for how practical it is, it possibly comes in a wipeable version.