Sounds like it's for car use, no?
If you are buying one just for use on LEL - could you not borrow one, or even rent one?
For in-car use, any of the Tom Toms would be reasonable. Arm yourself with the postcodes of the controls (if you are "car borne" in order to hop between controls) and let Tom Tom do the rest. They are pretty easy to use, but not infallible - I remember simonp's Tom Tom getting really confused in the Henley one way system (who can blame it?) once.