When I passed my big bike test a decade ago, I bought a 900cc Diversion, but found it a bit top-heavy and not too easy to handle at low speeds. I swapped it for a 600cc Yamaha Fazer and this really is a great bike for novices and experienced riders alike. It has half-fairing so is ok on the M-ways but is also light and easy to handle around town or country roads. Bikes of 125cc & 250cc etc are very unstable when you turn round to look behind you (an important safety technique) as the whole bike tends to wobble. You are better off starting at 600cc which give a nice stable platform from which to observe the motoring world around you. I had to get rid of my bike due to ill-health and haven't yet replaced it yet - I really do miss it and never had a spill despite all the doomsayers.