Thanks again everyone. I'm not on any meds that could affect blood pressure, so its not that any medication needs reducing. If it is blood pressure related I have read that upping my fluids might help so Im going to make a real effort to drink more over the next couple of days.
Ive woken up with a horrible cold and sore throat this morning so it could even be related to that I suppose.
Its not causing too much trouble at the mo, but will def mention it to the GP at my next appointment, or go and see him if it gets worse.