Those are very clever Dan, thank you. Unfortunately, the decent sized ones seem to be the wrong side of the pond and importing to UK / Europe would be crazy. I don't think the boat trailer manufacturer I am talking to would follow the lowering route, but two hinged ramps and a stowed centre ramp are not too onerous.
Loading would be less easy than with the types you have shown - and there are plenty out there. Driving up backwards could be entertaining, but winching up with a low mounted electric winch would be straightforward: I use one for shifting my 750Kg miniature steam road locomotive into its box trailer.
I may contact a UK bike trailer manufacture to see if they are interested. Thanks again for your input.
Tim
