I did have a site but iv lost it had a ranking system for UK suppliers im sure it was rommell or romell something or other and if I remember rightly scan.co.uk did rank quite highly there so does komplett.co.uk
If I do come across again it Ill edit and post the link
EDIT:
http://www.romulus2.com/feedback/chart.php?1
of course like all online rankings they can be manipulated so dont believe just the one place.