Unless you have previously indicated to IIB that you wish to revert to a tracker rate upon the fixed rate expiring, it will automatically switch to the standard variable rate.
IIB should contact you a month before the expiry to inform you of yoru options.
Also, once you come off the fixed rate and switch to variable or tracker, you can then change lenders and not incur breakage fees.
Shop around!!!
do you have to be on the variable/tracker to be able to switch without penalty
or does the fixed term cease when the final 'fixed' payment has been made.