I think the Cessna 337 should at least get a mention. If you loose either motor on take off she will simply climb at a much reduced rate, appx 150-200 fpm. A good one can be had for around £50k or if you look at the American market with the £/$ at over 2 you can pick up some seriously good planes for not too much money. Not sure on the procedure/cost of getting them onto the G Reg though? Also if your purchasing the plane the ferry pilot would be happy to take you along, if thats what you want to do. I would jump at the chance of a trans atlantic ferry flight.
Speeds are up there with the other planes, 165kn cruise and decent payload. I think the U/C can be expensive in maintenance though and a lot of people will say the rear engine suffers from over heating. This can be alleviated with some sensible ground handling, eg not starting the rear engine untill you are ready to go. Allowing enough time for warming up though
One other objection you might hear is that they are too noisy, the engines rev to 2800 and so the prop tips go supersonic hence the noise, but if you mention when calling for ppr that you will use 2500 for take off, assuming the runway is long enough, then you will allay most peoples fears of upsetting the neighbours!