you would be better off using johnstones aqua guard satin as your finish coat, the aqua guard is fully water based but it behaves more like oil when applying so you get time to work with it and it dries to a great finish with no brush marks. it does have its own undercoat but i use zinsser 123 ...
there's an easy way to deal with this, and you'll never need to worry about it ever again
http://www.bathroomcladdingshop.co.uk/ceiling-cladding
modern looking and easy to do
or if you prefer the old fashioned look, use timber cladding and stain it with a 7 year wood stain
par for the course with new builds
house bashers & obliterating emulsion spring to mind.
I wouldn't worry about it, once the house dries out, the cracks and nail popping starts to appear, so will need re-painting anyway.
then you can use a more durable emulsion.
there lies the problem,
too do it right with a proper stopcock, internal double check valve , drain cock, lagging, clips etc, would cost you around £90 - £100 mark.
sadly for a lot of people nowadays, it's all about the price
you can cut it with a multitool like a dremel or just use one of these
http://www.screwfix.com/p/irwin-mini-hacksaw-24tpi-12-250mm/36273?kpid=36273&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&gclid=CJLbpquxuL0CFUcTwwodyYkAtg