Thanks for fast replies. There are no obvious leaks around the water pump, the leak I've seen is at the front of the engine block, right under the distributor. There is also some corrosion around it so I guess its been leaking for a while, maybe explaining how I got the car with very little fluid in her. Could this explain the bubbles in the rad?
I've also noticed something else, when the bubbles start idle drops slightly. It lasts maybe 5-10 seconds max then I get no bubbles and the car just warms up normally. The warmer she gets the smoother she runs.
Quite confused at this stage to be honest, I keep thinking its the head gasket :/, which would be a major blow as I've already paid quite a bit for the car. . . (1 of only 3 Super S in Malta so considered a bit of a rarity)
I'm taking the car to a garage meanwhile to get an expert opinion, feel free to throw any other ideas at me in the meantime 
