Had you already been on max NCD, then i would have said your increase was perfectly normal, but because you should have accumulated an extra 10% NCD, then your company are obviously at it!

This is proved by the quote you obtained yourself being cheaper, although they will probably argue that they are giving you a new customer discount.
Talk to them, and they should reduce your premium simply by asking.
As long as nothing has changed at my end, i have never had a renewal invitation that i simply accepted and paid, because insurance companies routinely sneak in an increase and hope you just pay without questioning it. More and more people are getting wise to this now, and a discount rarely takes more than a quick phone call.
I see you noticed the thing you have to be very wary of with the cheaper than average quotes you get on the comparison websites - ridiculously high excess's. This is not confined to young drivers either, because i have experienced the same thing at 42.

I would never go for a slightly cheaper quote that had a high excess. I see it as false economy, because the only reason i buy Comprehensive insurance, is for the possibility of making a claim, so i definitely dont want to be in the position of having to pay out more than my total premium for the privilege.