Help. My beloved 100000 miler Disco 4 has a broken cam chain. Does this always mean bent valves and broken pistons? Is it worth taking the body off and hoping no real damage other than maybe a bent valve or two? Is it a right off?

The short answer is "It depends" but it'll deffo be a "head off" job or heads of if you have two.
Can you get that done without taking the body off?
Can you get the engine out without taking the body off?
This sort of damage doesn't always involve severe piston damage, sometimes they are just marked a bit, But new valves and possibly valve guides, maybe even damage to a cam or two.
Real shame and do feel for you.