I eventually found my old (15 year old) games workshop paints in the garage, most of them had dried out but some of the inks and washes survived. I did some research on the web and found you can resurrect them by using a mixture of water, Tamiya acrylic thinners and shaking the hell out of the pots. I can also recommend thinning them down until they can be poured into squeezable bottles. (20 bottles = £7 inc delivery - eBay)
The bottles are so much better for two reasons, 1) You can squeeze out exactly how much paint you require without using a brush, 2) mixing colours is now much easier. i.e. 2 drops + 1 drop = required colour, no more trying to mix and match.