Get off your butt and start finding out for yourself.
If it's any help, my multi-bike, central London, high mileage (no commuting or business use) reasonably significant accumulated theft risk (though garaged) as an employed (though divorced) 50 plus year old in an unmorgaged but owned property, with a clean licence, full no claims bonus quote from Devitt and the BMW Motorrad scheme was not too bad.
Yours, as a Brummie , pimple faced youth with two driving convictions and a further pending, limited no claims bonus with an ungaraged single (but highly bling'ed) steed used for daily commuting to Norwich to ply your trade as a travelling toilet brush salesman, might well be different.
Your own efforts will pay you dividends. Trust me.
Just renewed today. ( Fully comp, 9 years+ NCD cover, legal, Class1 business, 12000 miles a year). Old git - bike garaged overnight. £100, believe it or not (against first quote of £180).
Boy, am so glad that I have got the IAM (did it through their own brokers, IAM Surety/Cornmarket, who will virtually always match the best you can get elsewhere, as long as you do you some serious comparison website homework first.
Might even celebrate by buying somebody a lemonade!!