Basically you can in sure a bigger bike on provisional
But the limit is 25kW (33bhp) or to a power to weight ratio of 0.16kW/kg
So you could insure honda goldwing on provisional

if you take into account power to weight ratio
bandit 6's have to be slightly restricted afaik
But you will get quoted by insurance company's regardless, but insuring bigger restricted bikes like r1's, you will still be paying a much higher insurance due to the bikes insurance group.
I was going to get a cbr250 for the summer and was told by a guard that it was ok un-restricted on provisional but many others would say that's illegal so it's a bit of a grey area imo.
I say if your taxed and insured with your licence and be nice to the guards you'd be fine.
BTW you have to wear a yellow jacket with giant L's on your chest and back. HAHAHA!