Thanks for all the comments/discussion!
My, uneducated in this area, thoughts were that the soot had been building up over time and that the few days before it became smelly, it had been pretty windy. I originally was thinking that it 'just' needed servicing/cleaning, so was quite...
Hi, my first post so if I say anything I shouldn't please let me know and I'll change it accordingly.
Basically, noticed that the back boiler in our dining room was smelling a bit gassy, when on and there looked to be soot around it so got in touch with BG who sent out transco, who turned it...