Lots of info on the Mog 3-wheeler here:
MorganWest Morgan Cars - 2011 Morgan Three Wheeler
Base price ~$40K
2011 Morgan Three-Wheeler - Top Speed
There is also a US made version built in Seattle under license
from Morgan. Price: $48K and up!
Ace Cycle Car
The "cycle car" has a long and venerable history in the UK as a way
to get on the road without incurring high taxes. The situation appears
to continue today with what are now called "tricycles" enjoying a
relatively modest annual tax as compared to 4 wheelers.
Vehicle taxes for cars, motorcycles, etc. : Directgov - Motoring
FWIW, I will admit to a deep seated, irrational affection for the
antediluvian Mog 3-wheeler and its derivatives. Maybe it has to do
with the engine being featured so prominently. Sure, it's anti-FE, but
it makes fiddling with the engine -- an essential part of motoring
back in the day -- a simple matter.