My suggestion would be perhaps to consider replace missing lead with LEAD FREE FLASHING THAT DOESN'T COST THE EARTH Eurocell Building Plastics launch Ubiflex from Ubbink (UK), a waterproof flashing material that can be used in all applications where lead is traditionally installed.
* Read more: http://www.buildingtalk.com/more/7448/

On reading the full article it seems to be environmentally friendly and has no scrap metal value !! I have no commercial interest in this product but wanted to bring it to light in the current wave of theft from church buildings etc.

Just a thought as I spotted this news release

Why do I think that, at the first rain, this is going to be washed away like so much dust ?

there was a plague of stealing metal stuff from public places here in poland couple of years ago. railroad tracks, electric transformers, sculptures and monuments etc, for obvious purpose.The plague ceased mostly because there was nothing more to "collect" that was not welded to the ground. With recent wave of migration from poland to UK i think i can guess who's the culprit :)) think green, collect garbage lads!

Paying tens of thousands of pounds in repair bills versus pocketing 5.25 million from the insurance companies, not a bad deal for the church...