Myself and my business partner can drive anything 24-7 fully comp (as long as we have a license for it), business or pleasure and list as many personal cars on the policy as we wish (MID). All we have to do is ring them and for-warn them if we're going to drive a vehicle over £100k (yet to make that phone call). Also covers up to £100k of cars in garage, £85k of tools, employers liabilty cover to £1m and public liability to £2m!
£2100 pa for 2 business partners and any member of staff over 21 (business use only) - Aviva
Makes you realise that regular car/bike insurance is a total rip off!!