Also if you have too much paint on your roller it leaves marks. The trick is to go over the same area in different directions

We used to own an old farm-worker's cottage with a separate, single storey coal/laundry building behind. We connected the two buildings with a rear hallway link building and gutted the coal/laundry shed to convert it into a new kitchen. We removed the old ceiling, put veluxes in the roof to add light and also kept a few of the joists (we removed some of them but had to put strong bolts through the remaining ones to tie them to the rafters.) We also put collar-ties on some of the other rafters and put extra reinforcements in along the wall-plate. Bottom line, is, I think it's well worth opening up the room into the roof pitch – it will look fabulous – but you should probably have a word with a good structural engineer first! :-)

Skimming a wall isn't a job for the average person even with DIY experience. You really need a plasterer in to ensure it’s all level or else it will show out and you will find yourself constantly looking at it. When it’s painted it will show up any unevenness.

I know, cutting in is a nightmare. I’ve even used frog tape which worked until I removed the tape and took some of the ceiling paint with it! I think all one colour will work well if you use a pale grey like Dulux Polished Pebble or F&B Ammonite. In the picture below the person used F&B Cabbage White on walls and ceiling.