Home Insurance providers and hikes

Probably thought this was the best sub to ask this question due to many others with high-value housing.

We have had buildings and contents insurance with the same provider for the past 7 years. We started out at around £600 per year, and then had a very large claim for an oil leak in our first year, although premium didn't increase by much over the next couple of years post-claim. We now currently pay £2400 (with 5 year NCD) for the year, and just received our renewal quote for £5000. This is the first year where our one and only claim no longer gets included on our policy statement of facts, which made this hike all the more surprising.

Obviously there are too many variables to note that affect the premium, but ultimately we have an old (but unlisted) house, of normal construction. Very large with 7 bathrooms (which I know is a big consideration for many providers, and many won't provide for those with over 5). We have unlimited buildings cover, contents cover set to around £50k, out and about cover for around £25k worth of items, and accidental damage cover. Excesses set to £1000 where possible. Even without all that information, the sheer hike in cost seems insane. Is this the norm? I have tried a quick search on comparison websites, but very few providers will even cover us, and we also weren't able to explicitly search for unlimited buildings cover, or dictate a rebuild cost of £2mil+, so even those quotes we could get were perhaps not comparable to what we currently have.

Question is: assuming you have a high value property, what sort of cover do you have? And what is your annual cost?