We have a couple with Aviva and another coupke with Adrian Flux. We've used Be-Wiser before now but they use proper salesmen (as in agree to anything, tell you anything then when you get you paperwork through and check it it's not quite what you expected).
Aviva are a joke with existing customers and for this reason every other year we have to switch.
As with all insurance you've got to dedicate at least a long morning to ringing around.
