Thanks Jonathan as ever.

I'll try with some liquid coolant next and see how that goes - reason I thought I was being a numpty in the F&S dept. is that most calculators are throwing up higher feeds generally e.g. 18-1900 mm/min, which I can try but that sounds aggressive, although maybe its not aggressive enough?

Must try and remember where I got my last batch of mills from, I'm likely to be placing some more orders ;-)