Laid-up insurance

Having just got a new lockup, I'm wondering about laid-up insurance. Never bothered with it in the past, but as the world gets more hazardous I wonder if it might not be such a bad idea. I know the major classics insurance firms offer it, but I have no idea about premiums or what detail of cover is sensible - tools, individual large tools like trolley jacks etc. Spare parts - spare gearbox yes, jar of nuts and bolts - probably not!

The garage is 14 miles from home so I'm not going to be checking it every day. How do I reconcile any security the insurer might insist on with the rental agreement that says I'm not allowed to change the locks or add any new ones?

And how do you value a car that's in bits?

All thoughts, comments, experience and advice most welcome!

Thanks