I've just finished a job using Cannon & Ball paint . The cost of 5 lts of estate emulsion was �48-00 !!! This was from Homebase. The quality of the paint is poor, that is to say it covers well, but scuffs up badly, especially round light switches etc. You'll also find that it doesn't wash-down very well. So, if you've got kids or pets in the house you'll be redecorating every year.
If you've got a Dulux Decorators Centre nearby I'd go in there & look at some of the 6,000 colours they have to offer. Then get it in the trade range.