Call 0800 862 0331 and ask to speak to Dan (Say Hedley recommended you).
Quality service, superb support (they also offer white label support via your WHMCS customer portal so you can offer 24/7 support to your customers) and excellent prices.
I have been happy as a pig in muck since moving to these guys. They also offer a free WHMCS licence with their reseller package which is a godsend and a huge saving on a lot of the other companies around there. WHMCS allows you to manage your entire billing & invoicing, domain registration, support ticket system and knowledgebase.
They were and may still be running a 25% off and free upgrade to next level offer on one of the Web Hosting forums which I can't remember just now but can hunt for it if you are interested?
EDIT: webhosting.com is where you might still find the offer. You have to create an account first to be able to see the offers section but it is well worth it.