We host our own sites on dedicated servers.
However, we do point clients who are after shared hosting to two companies:
SiteHQ -
www.sitehq.co.uk
YSH -
www.ysh.co.uk
Both are very good, and listed in alphabetical order - no preference!
Although I have recommended them both for years, it would be pertinent to mention that Pixelcraze has done work for both companies in the last 6 months. This hasn't affected who we recommend people to, as if we recommended a host that was bad, it would look bad on us!