For espresso, Hasbean's Jailbreak is excellent. For French Press or pour over there are plenty to choose from as a blend isn't necessary. There's a great Mexican light roast currently available at the Wholefoods market; £3.99/kg. I've tried Red Brick and think Hasbean offers better value. Markus Coffee also do some good single origins but also know how to put a blend together for Turkish and Ethiopian/Eritrean style coffee. Places like Monmouth just don't have the broad knowledge to help with that.
Mmmmm, Jailbreak.