***UPDATE***

Out at lunchtime, water I put in earlier was still in and had no leaked so assumed couldn't be a leak, anyway it is stillgetting too hot I even took it up the motorway, at 80, it was at the bottom of the "N" when normally it will be on the "M" at that speed, with all that air and the fan on it was not cooling down, so guess it's fucked the head gasket? Water looks pretty dark, having the heating on full blast seemed to help a bit too... all though no other tell tale signs as yet Wot you suggest I do?