Thanks for the reply again, I am a bit out of practice with polar coordinates at the moment but will look over this. In the mean time I have applied another method with is giving reasonable results <1.5% error from the worked example I am studying. I can calculate the equation of the curve, which I have done in excel for the polynomial which is attached (just done this for speed).
Then integrated as shown in the other attachment, is this correct too, my maths is a bit lame atm