Not a lease finance, but my former E63 was part financed with Mercedes’ own finance and last July I paid off the remaining balance which was 9k + I think and not only did I get an email confirming they received the money, a text within a few hours of it clearing at their end, but also posted confirmation through my door a few days later, this during lockdown. It was pretty simple once I managed to get through after an hour or so... I didn’t pay by CHAPS mind, just a direct bank transfer from my account to theirs. I had more hassles cancelling the direct debit with my bank at the time IIRC. I do remember my bank sent a text asking if I had made the payment due to it being a large sum which is common of course and kind of reassuring in this fat and age of fraud.