\\\\\I'm taking tablets to regulate BP. Could it be they're working too well?\\
Working well...........yes, but not necessarily too well.
\\\ Is a visit to the GP called for?\\
No.
Bottom line: you are on BP tablets, you are not as young as you were, it is taking your body a little longer to adapt to the upright position, so get used to it.
Don't jump out of bed, sit on the edge of the bed for a couple of minutes and then get up and move off.