Bank of Scotland levy a charge of €95 if you wish to change the terms - e.g. increase or reduce the monthly payments to your tracker or variable rate mortgage. The financial ombudsman has recently ruled that this charge is "possibly illegal". The upshot of this is that if you ask BoS to change your repayments and they refuse you can complain to the financial ombudsman. He can then award compensation. I am aware of sums in the region of €500 being awarded - not too bad for 3 letters!
Afaik, once the charge is flagged in their T&Cs (or in the Loan Agreement), there's nothing illegal about them. But I'm surprised that they're seeking this fee just for upping your repayment amount — unless you're in a fixed-term agreement?
My own mortgage used to be a BoS tracker, and I seem to recollect that this €95 fee only arose if you wanted to switch 'product' — i.e. from tracker to variable, or vice versa.