Scheme and processing fees go to Visa and Mastercard for running the rails. They are not capped, and the regulator has said plainly that competition here is not working.
Core scheme and processing fees charged to acquirers rose by at least 25% in real terms between 2017 and 2023. The regulator put the extra cost to UK businesses at at least 170 million pounds a year.
Find the scheme fee line on your statement. If you cannot find it, your pricing is blended and the next lesson is the one you need.