In December 2016 they reduced my monthly repayment.
An overcharge accrued when in arrears remained on the mortgage until this week, at which time my monthly repayments reduced to €1,000 per month.
These are illustrative figures but in the general range of the amounts due!
Timeline:
December 2016 repayment: €1,450 per month (on SVR)
January 2017 - December 2017 repayment: €1,170 per month (returned to tracker, but with overcharge still in place)
January 2018 repayment: €1,000 per month (overcharge removed from account)