I have re uploaded statements to QF and all transactions are accounted for and tagged but the two balances are different by £79.95 thinking of deleting account & reentering all transactions bit of a pain 5 months worth, any suggestions on what else i could try.
Just keep going back month by month checking balances. When they are aligned again you have found your month with the error in it, repeat with weeks & days if required.
I would suggest first checking the opening balance has been set correctly on the account settings screen in QuickFile.
Then I would follow the advice @Lurch provides, just keep going back until the balance is correct then iterate forward until you zero in on the exact day it goes out.