What is the mass of copper in Oxford's lightning conductors?

This is a view of a spire on Exeter College from Broad Street . You can see Anthony Gormley's Iron Man sculpture on top of Blackwell's Art bookshop. They'd even put a Santa hat on it! So I looked at the lightning conductor. Say 30 metres long and with a cross-section of 2cm x 0.5cm. The volume comes out at 0.003 cubic metres. Copper has a density of 8960 kg per cubic metre. I was surprised - that is more than iron! 8960 x 0.003 = 27kg. Now how many spires are there? Can't find that on the Internet. Say 30 colleges. That would almost give a tonne of copper. But many buildings have more than one lightning conductor. Then there are churches and mosques... Oh and what counts as Oxford? So some defining of terms to be done...