Hey,
Lots of decent advice here already so I'm only going to give you two pieces of advice:
1. Use Jonstones CovaPlus - you can get any colour matched with it too.
2. use a decent pole and roller frame for your roller - despite the size or height of the area.
Decent coverage and even looking finish comes from consistent application - holding the handle of the roller by hand and doing short 2' sections takes ages, looks messy and doesn't give good results. Instead, paint a section about 2-3 roller-widths wide
from floor to ceiling with one loaded roller. there's plenty of videos on youtube showing how you do this but essentially paint a big
N shape to spread the paint ont he wall and then fill in the gap by going the other way. finish that section by running the roller in the same direction the full height of the wall. start the next section with a slight overlap and back-roll to blend the seam.
it's a common mistake to think that poles are only useful for ceilings and high places - they're absolutely perfect for walls - even short ones. my frame has never been taken off the pole.
I use this one:
http://www.redlinebss.co.uk/fat-hog-roller-extension-pole-2-4?filter_name=pole (you really don't need the longer one)
it's from Jonstones' there's others like it but what's important is that it is thick, light, and locks into place. the Purdy ones are also great but a bit more expensive. Both I've mentioned are made of fibreglass and aluminium so they're very lightweight but much stiffer than those horrid steel ones you will get from B&Q
I also use a US style roller frame - which is very important too. the steel wire that bends around and goes into the roller is much thicker than a standard-issue frames so you get a much more consistent spread as there's little flex / bias towards the roller pressing harder on one end.
I do use a tray, rather than a scuttle but I have a Simms tray with a Tray arm, and I use the tray liners that go with it. I can highly recommend this if you're doing a lot of painting. I think I'd use a scuttle if I was painting an entire house one colour over a few days, but for single rooms I think a [good] tray is the way to go.
http://www.decoratingdirect.co.uk/viewprod/s/SIMMS_TRAY_ARM_KIT/
In fact, the image in that link is a pretty much ideal roller setup. it doesn't get much better or easier than that! Don't look at it as a gimmick; it's not.
if you have a cageless frame then this is not an issue, but not many DIY folk use them.