I recommend checking out http://uk.webhostdir.com and click reseller. Be sure to check that the UK hosts servers actually are in the UK if thats what your after.
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I don't mind paying for WHMAP myself, but the domain reseller account would be ideal as I don't have the capital to pay the $xxx startup fee's for my own...
I know a place that's very very reliable and quality, but it's a tad "expensive". It's cPanel/WHM, UK based with a great reputation. I know this isn't exactly what you were looking for (without WHMAP, domain reseller... etc) but I'm sure one of the other members would give you a domain reseller account. At least check them out, and read up on some reviews Been with them 2.5-3 years now.
I'll keep my eyes open for your exact requirements, though. Good luck!