I recently spent many hours poring over websites and insurance policies and filling in quote forms for my newly-acquired 2014 Cali Ocean. I thought some feedback might be useful for other new owners looking at comparison quotes (exact quotes will vary greatly between users of course).
I found cheapest specialist campervan insurer was Just Kampers (under £400); next (£400 - £500) Comfort (who no longer offer specific VIP discount), Safeguard (who do offer club VIP discount) and LV; Saga (£500 - £600) then Camping & Motorhome Club (£600 - £700 - which was disappointingly high as I'd insured my caravan with them a few years ago). I also spoke directly to several of them to quiz them on their policies. And I looked at online reviews regarding claims performance.
These specialist campervan/motorhome policies generally seemed to cover what I'd expect under normal usage and holiday conditions, in my opinion. I chose Safeguard in the end and was happy with their coverage (which included European insurance and breakdown cover). I found their call centre easy to deal with and helpful on the couple of times I called them, which I think is a good sign. I think Comfort and LV (best designed web form) would have been good alternatives for my needs.
The comparison websites seemed pretty useless for campervan insurance, so you have to do the fingerwork around individual websites if you want to find several quotes. And it can be difficult to make exact like for like comparisons between different insurers. In the end, though, I found speaking to insurers directly was more productive than just submitting web forms.