When I worked for Company of Cyclists, we had a Giant Lafree, the forerunner to the Twist, and it was lovely, but I don't know how the more recent models compare.
Have you had a look through Electric Bike Magazine? Free to read online, or you may be able to pick a paper copy up at Cycle Heaven, I think.
Electric Bike Magazine: the independent guide to power assisted cycling(yes, I work for it, but I figure as you can read it free, it's ok to plug it...)
There are plenty of dropped top tube models, and currently you still have the option of pedal assist (where you have to be turning the pedals for the motor to work), and the throttle type where you can, if you wish, just power along without pedalling - the latter type isn't allowed in Europe, and legislation may well standardise in the UK too, although it's unlikely to be retrospective, so anything bought legally now will stay legal.
As with any bike, test rides are much recommended - there are the usual issues of fit and posture, and then there's the ease of use of the assist, how smooth the throttle is, how easy the battery is to charge etc.
