In reply to Ffati1:
Also use Brentacre.
Like others, I haven't had to make a claim but so far they are very easy and pleasant to deal with both by phone and email. Get straight through with no menus on the phone and respond to emails within an hour or 2 during working hours.
When I was looking for insurance the main appeal was that they clearly cover converted vans that the DVLA classes as 'Panel vans'. This was a grey area with some of the other insurers that I looked at.
They also seem to be competitively priced.