Thank you all for your replies and suggestions. I have suffered with low iron in the past and feel exactly the same now as I did then. I am getting a bit sick of going to the doctors what with one thing and another over the past few months so was trying a bit of self-diagnosis
Maybe with hindsight not the best idea and one of the symptoms I have had previously with low iron was a loss of hair (ie it coming out in handfuls!!) and that was when I still had a regular period. I haven't had a bleed for nearly 3 years and this time the hair is staying firmly where it should.
Perhaps another trip to the docs is called for just to be on the safe side x