Decorating Centre Online is BRILLIANT for paint. They will colour-match basically any colour from any 'designer' paint brand in a range of finishes. I recently got a colour-match from them in the standard wall paint and it's the best quality paint I've ever used, it only needed one coat and went on like a dream. The Valspar colour-matched sample I got from B&Q was really runny in comparison.
Shade-wise, if you don't want yellow or grey undertones then Pure Brilliant White is your best bet, but Timeless or Rock Salt by Dulux or Wevet by Farrow & Ball would be good if you didn't want to go down the WHITE white route.
Let us know what you go for/have gone for