Thank-you so much for your help. I'll see if there is a rescan database option or something.
Just to double-check I did the double-spend correctly. I just sent the exact same amount to the same address with a larger fee - is that correct?
Just out of interest, the unconfirmed transaction never seemed to appear in blockchain as far as I could see, only in bitaps. This was even before I did the second transaction.
Just to clarify, the 1st trx did not go through. The second one did. If that makes any difference.
Actually you didn't double spend.
Your first transaction had 2 inputs. While your second transaction had 1 input. The inputs values of both transactions do not match.
However your first transaction will probably never confirm as it was sent with 1 sat/byte.
Most mempools will drop unconfirmed transactions after 72 hours, so you just have to wait.