I'd be up for this one definately!... We drove across America a few years back, and even with the distances covered, it was one of the best trips i've ever taken.
The circumference of the UK is ROUGHLY 2500 miles, so from this you can easily work out how many miles you need to run in a day.... if you have a duration!
Assuming that everyone works / has family / has other committments, then i would guess that we are looking at a holiday type timescale.
Quick maths...
To do it in 5 days, we'd need to travel 500 miles a day
To do it in 7 days, we'd need to travel 357 miles a day
To do it in 14 days, we'd need to travel 178 miles a day
The other handy thing would be if everyone interested in going had Autoroute. We could then e-mail the route around, and add home locations, meet up points, pubs to head for, pubs to avoid, pubs that do accomadation, pubs that let you sleep on the bar, decent off licences, petrol stations that sell beer .... etc