Calculated (calculation based on other columns) IF OR ISBLANK AND Sharepoint Lists error formula

Question

Can anyone help? I can't work out why this is erroring. this section =IF(OR(ISBLANK[Tech £]),"", at the start in bold makes it error.

=IF(OR(ISBLANK([Tech £])),"",IF(AND([Tech Pay Type]="Paid in Full",[Tech Pack]="Pack 2=PC Only"),"0",IF(AND([Tech Pay Type]="Paid in Full",[Tech Pack]="Pack 1=Full Kit"),"0",IF(AND([Tech Pay Type]="Paid in Full",[Tech Pack]="No"),"Oops",IF(AND([Tech Pay Type]="N/A",[Tech Pack]="Pack 2=PC Only"),"Oops",IF(AND([Tech Pay Type]="N/A",[Tech Pack]="Pack 1=Full Kit"),"Oops",IF(AND([Tech Pay Type]="N/A",[Tech Pack]="No"),"0",IF(AND([Tech Pay Type]="Monthly",[Tech Pack]="Pack 2=PC Only"),"£23",IF(AND([Tech Pay Type]="Monthly",[Tech Pack]="Pack 1=Full Kit"),"£40",IF(AND([Tech Pay Type]="Monthly",[Tech Pack]="No"),"Oops")))))))))