I've looked at the ingredients for M&S scones and they use buttermilk, unsalted butter and a little clotted cream. No vanilla essence.
Buttermilk is easy to make https://cookieandkate.com/buttermilk-recipe/
Adjust any good recipe to include those ingredients and you should be happy with the results.
Scones are so easy to make and absolutely delicious when still warm from the oven. Shop bought scones can't compare.
Give it a go and send me a couple :) Jam first, always