Now it's not often I ask for help, but here I am!
Leaving work this evening, I decide I may as well check all my (car's) levels. Doing so, I notice that to my horror that the coolant resevoir is actually empty! I check my coolant level once a week, and it's never dropped anywhere near that much. Well, I top it up back to the maximum mark and set about investigating (well as best you can for fumbling around in the dark with a torch!)
[A bit of background information - I have since owning the car needed to top up the coolant every few weeks or so, not sure if this is related or another issue again, but I thought I should mention it in case.]
Set about checking the bottom of the radiator/metal sill running underneath, and sure enough, there is some coolant sat in the metal. (As you look into the engine bay from the front of the car, it is on the left hand side at near enough the left edge of where the radiator is mounted.) I can't say that I have noticed this being wet before, and I don't believe it to be from the ice on the car thawing out as that happened yesterday and it hasn't rained since.
So now I am at an assumption that I need a radiator. Obviously I shall do a more thorough check tomorrow on my lunch break when it is light, but I think it will only reinforce what I think already.
I know that a hole in the radiator would explain the sudden fall in coolant level, but has anyone got any other possible ideas before I part with money....