Yeah shut off valves are the obvious next steps, but I think the reason they haven’t really taken off with the insurance schemes is exactly as you articulated - complexity and cost. In the US it’s easier because stop cocks are commonly those lever ball valves (which you can easily retrofit a control box to, requiring no plumbing work) but here those silly little twist taps are still really common. Not to mention most of them are hard to access, buried in walls, are generally left with very little space around them, like you said.
Home insurance is so price driven - average in the UK is what, £150 per year? So throw in a few hundred quid for the valve, plus the plumber’s time and the £’s don’t add up. Plus the price comparison sites are making people switch insurers more often than ever before, so what happens when the customer jumps ship at the end of their policy? You lose any long-term claim benefits, making the whole exercise pretty pointless.
Stand alone leak sensors are better than no leak sensors IMHO. Let’s say the average house is occupied approx 65% of the time (assuming the occupants work 8 hours a day, 5 days a week, plus out for a few hours on the weekend). That means you’ve got a 2/3 chance of being at home when a leak occurs - allowing you to go and deal with it. And even if you’re not at home, you can deal with it with nominated contacts (neighbours, friends etc) or by just coming home. Providing you can respond within what, 10-15 mins? Damage is going to be pretty minimal - if nothing else you’ll have reduced the claim amount significantly (also reducing the disruption to the occupant.)
Of course for some people, they WANT to have a shutoff valve for extra peace of mind - cool then there are solutions out there for that. But I can’t see UK insurers ever really swinging for it on a mass market scale any time soon. Maybe in the higher end of the market? People who pay say £1200 per year and up? I can see that, because the £’s make sense. Spending £300 to stop an escape of water claim in a home where the solid wood antique floor alone cost £30k makes more sense than doing the same in a house with a £300 carpet. (Slightly facetious example, but you get the idea)
Or perhaps someone will go for a model where the user pays for the valve cost upfront, and gets some sort of ongoing discount on their premium as a result. That could work, but it’s still a big upfront cost (£400 all in upfront to save 10% (£15) per year.) I suppose it’s more about the peace of mind… but if that’s true why aren’t more people just buying them in the first place?
I’ve actually been saved twice by my leak sensors - both times I was at home. One I put a load of washing on and got a sock caught in the door (breaking the seal slightly) and resulting in it pouring onto my kitchen floor. The other time (coincidentally, also related to the washing machine) was when the waste water tube came loose from the fitting on the back of the washing machine, again resulting in water everywhere.
Those two times alone have convinced me that these cheap, simple little sensors really do have a place in the home. They’re absolutely not perfect - but in the land of the blind, the one-eyed man in king. So to speak.