Hello RedOnion, RETIRED2017 and Brendan,
Well, having phoned Pepper today I can confirm it's not a mistake on their part, or a lodgement by someone else wrongly credited to my account. Despite applying all of my small top-up payments as I've made them, they're doing this as a 'housekeeping' tidy-up on my mortgage, so I get to choose whether to reduce my regular monthly repayments by over €100, or shorten the term of the loan by 14 months.
I told them I'd think about it over Christmas and get back to them in early January (right now, my instinct is to shorten the term of the loan). Any thoughts from you on which might be the better option?
Thanks, Molly