Erasing the big blue mistake

My lounge is big and bright with floor to ceiling windows looking out over the front garden. I made the fatal mistake of assuming such a bright room could 'hold' darker colours - it didn't suit and it didn't work.
This was how I lost my colour mojo. I've never made a mistake like this before and what a BIG one it was. Painting a room you live in, with children in the house is nothing but shenanigans.
First all children must be removed from the immediate and local area. Preferably to the grandparents. Then all furniture must be moved around and covered. THEN you can begin prepping the walls.

I am the Queen of Shortcuts and innovation when it comes to house tarting and fixing, but I find that doing 'longcuts' and preparing properly is actually the shortcut.

The walls must be clean and free of dust. You can lightly sand it down like did, or just give the walls a good wash with sugar soap. Wear gloves because it's strong stuff.
Mask all the edges to keep the paint in. Along skirting board and around power points etc. Do not use cheap masking tape. I did last time wrongly assuming it was all the same stuff and I spent a long time trying to pick random bits off the boards.
There are stacks of different kinds of tape for this now, you don't have to go overboard, just not too cheap.

Here I have 'cut in' the undercoat. You do all the fiddly bits with the brush where rollers etc won't get in properly. I've only had to undercoat because both (horrible) colours have such a dark base. Usually you can just paint over the existing colour. Fill in any holes at this point with filler. I don't use fandango applicators for filler - that's what fingers are for.

You can see my random patches of other colour here. I was quite taken with the new metallic colours available but they are just too dark for what I want.