Did your NHS clinic say why they wouldn't give you a DATscan, when your neurologist had recommended it? I find this very strange. I know that not all hospitals have the equipment installed however. I enquired about having a DATscan done privately 4yrs. ago when first suspected of having PD and my neurologist said it would cost £3,000. Had it done on the NHS in the end.
I would make a fuss and ask your GP to intervene. You need to know whether you've actually got Parkinson's or not, for your own peace of mind.