Thank you both for the replies. It's good to know it's a condensing type (I assumes the pipe at the bottom is a condensate pipe which is how you knew?).
I'll check the loft for header tanks when I next get in.
It's good to know it can't be too old - seems like the grant vortex condenser types...
We've moving into a new house with an oil boiler and I know very little about theses systems. The sellers are elderly and getting details on how the system works is proving tricky. They have it serviced etc and says its all in working order, but I'd like to understand what I'm going to be...