Try Zurich. They are expensive, yes, but on our policy we can't be underinsured, so you don't need you worry if you buy a new machine or two.
I've only had to claim once, when a cupboard-full of ironmongery fell off the wall and landed on my planer-thicknesser. I wanted someone to come out and set it all up again, but they wouldn't, they just sent me new P/T. I should have been delighted, except the machine was a Friday afternoon job! However, Kity did send an engineer round, and 16 hours of work later I had a perfect machine.. But that's another story.
Just one thing with Zurich though, and it might be the same with other insurers too - if you do claim they load your premium very heavily. We've had 5 claims in 16 years, but the trouble is that 3 were last year. We got burgled, then a week later we got hit by the rains, then the day that episode was signed off our washing machine inlet failed and flooded the kitchen. Now our premium has been loaded 30% for 2 years and no-one else will touch us. It was a big premium to start with, so now we are paying over £100 per month, house and contents.
So it is available if you can stand the price, and actually we can't fault their service.
S