Hi Paul,
Our boiler is virtually new - so shouldn't cause too many problems
The rest of the system is getting on a bit - so far, touch wood - no leaks but ...
You can't just get insurance for the radiators (from what I can see) - so home insurance that covers the lot (£500 max) - should be OK - plus it is a whole lot cheaper than an extra £250 for full cover - My quote (buildings & contents) is only £138,,