when I phoned them up, I explained that I was looking at a screen with exact same policy cover for hugely less than their renewal quote. I explained that I was quite happy to cancel and renew online, but the guy was keen to do the deal on the phone. I gave him the quote reference for the online one, he verified it and job was done within 5 mins. Didn't have to change any details for the direct debit or anything, so very straighforward.
I queried as to why the renewal quote was so high, which he couldn't answer, but interestigly did say that in some cases the quotes they send out were less than new online quotes, which ties up with some of the other posts.