I had done some reading prior to buying the car about the lambda light and is being a general engine management light which could be anything, I guess I was going to try the sensor first as the seller specifically said it was the sensor, but thinking about it they may have just made the assumption based upon the warning light being the lambda sign.
Great advice guys, this is exactly why I like forums and appreciate your time and expertise.
So I think I need to get a reader, which makes sense. In terms of the diagnostic port it is an OBDII as I have seen the wording on the coin holder and, while cleaning I pulled the holder out and could physically see the little port underneath.
I believe I will go with the flash code reader route, by the sounds of it it is something similar I had on my old MX5 where it plugs in to the port into specific port holes (or whatever they're called) and then you have to count the flashes which then relate to a specific fault. Clever stuff.
I stumbled across this while wandering around the forum, is this what you did Mr 4x4?
https://www.volvoforums.org.uk/showthread.php?t=83897