IF function using WORKDAYS and a Bank Holiday list - trying to add new holiday dates

Hi,
Hoping someone can help.
I have 'inherited' a spreadsheet from a colleague that has left the company and I am trying to update a function.
Basically, we have columns for
Start Date - Which is set for staff to enter a date
Automatic calculation of due date - (IF formula to calculate 10 working days from the 'Start Date', so excluding weekends and bank holidays.)

Now the bank holiday list that we have embedded in a separate sheet only went up to the start of 2013. So I am attempting to change the formula to look at a longer list of bank holidays.
I am pulling out my hair trying to get the formula to accept the new data set. I have tried manually changing the new cell it goes down to in the fx bar (i.e. A3 - A38) but it keeps reverting back.

I can't remember how to 'set' the Bank Holiday list with regard to working days function.
Any suggestions?

TIA