1 and 1 offer the cheapest UK domain names with prices starting from as little as £0.99 Their current offer on hosting is very good too with just £2.49 per month for the first 3 months. Even with a 12 month contract this makes it considerably cheaper than most other hosting. No discount code is required for this offer.
In our experience, they are reliable and have up-front pricing on both domain pricing and hosting. Tech support is via email or a local call rate number. Despite the number taking you through to a call centre, the quality of support we received was generally higher than most registrars. Support emails tend to be replied to within 24 hours.