Wickes vinyl emulsion problem.

[Roverload]

My mrs bought some filthy cheap paint from home bargains, I was sceptical, apart from it being nowhere near the colour it said it was, it was fantastic! So came to do the kitchen and thought I'd be a smart arse and go to wickes instead, I bought 5 litres of wickes vinyl emulsion, started painting it on and have noticed this:



A lighter strip shows around the window sills, what is this? I now remember painting the bathroom with the same paint a few years ago and the same thing happening, it appears to be something to do with the surface underneath but surely that can't make that much a difference? Any advice how to stop this because as my mrs points out, I have 3 days left to finish or it'll be my nuts roasting gently by the fire!

[Roverload]

That photo is after 3 hours drying, just got up and it's a little more obvious. I will try some of the suggested products and report back!

[Roverload]

Got it this morning from screw fix oddly enough! Cheers! Just stuck a coat on now, quite difficult to get an even coat because it's so thick! Like painting with treacle!