Back from the blood nurse - I can't spell phlebotomist! :o)
It was a different nurse than I had on Friday and she had no problems at all finding a vein. Phew! It was all done so quickly it was wonderful - if giving blood is ever wonderful!
I asked her why I needed to get the test re-done and she said the PV was raised and they just wanted to check it. PV - plasma viscosity - is what they're checking to see if I have any inflammation inside me.
So now we just have to wait and see if I get called back again for yet another test or if we just have to wait until next Friday to go and discuss things with the doc.