You can complain directly to your lender at no cost. Under the FCA redress scheme, once it is operating, lenders are required to assess eligible agreements and contact customers who may be owed compensation, whether or not those customers have complained.
Parts of the scheme are suspended until the Upper Tribunal has heard the legal challenges in February 2027, so no compensation is being calculated or paid yet. Your lender must still log your complaint and tell you where you stand.