Last summer I had DMG roofing out to my tenement to fix missing / broken slates, and they replaced my old cast iron (I think) roof light with a new one at the same time. If you’re just wanting it replaced, I’d try them - they were very good. [Here’s some pics](https://1drv.ms/f/s!AkHgppy-9Mke-QL_1eBPLR60NaVD)