Fix Leaky Sunroof On Jeep Freelander?

A 2000 JL F model, has a sunroof (not in use as the beading needs replacing which will cost more than the car I'm sure) which leaks intermittently. Not sure what sets it off but I get back to the car with a wet drivers seat.

Any ideas on how to DIY this fix? Or should I spend the extra to get the roof fixed. Not sure the rubber sealant is old and warn either.