Having worked in the web hosting industry in the UK for nine years I have seen a lot of brands come and go. I am still involved in some web development work and have set up sites for a few businesses and charities over the past few years. This puts me in a good position to recommend companies based on either personal experience or inside knowledge of how they are run.
Here is my list of recommended UK web hosts:
Hostroute
I have to confess a personal interest here as I founded the company. Although it has changed hands twice it still has some very good hosting plans - particularly for reseller or multiple domain users. The new owners have invested hugely in making the service reliable and with good support structures.
Here are a couple of voucher codes for money off Hostroute web hosting (use them in the order form):
GordonH 20% off web hosting
GordonHReseller 25% off web hosting
Blacknight
I use Blacknight for the hosting of my work web site and I have used it for several other web sites. Reliability is incredibly good because they use a clustered system (separate mail, web and database servers) and support is very responsive and helpful. Although the company is based in Ireland their connectivity to the UK is superb and hosting in Ireland makes it slightly more difficult for someone to take legal action against you for something you may have said about them. For that reason its a good choice for bloggers and they have a lot of Wordpress experience. The slightly complex control panel system can take a bit of getting used to (see this article) so it might be better for hosting of single sites that need good reliability. Highly recommended.
Xavvo
I know the owner of the company and it is a well organised set up. Providing cheap web hosting aimed at the UK market. Worth considering.
Mini VPS
This is the VPS brand of Xavvo providing VPS servers at remarkably low prices with high reliability (based on their independent uptime statistics). If you need a VPS this is somewhere worth considering.