I have large feet and often damage the shanks on the heels of my boots. I generally get a pair of boots reshanked (the shank is a metal strengther supporting the arches which runs from the heel to the midsole and which the heel is attached to) with larger and better quality shanks for £18 here in London.

The heels feel much more firmly attached after I've had this done that they did when new. I'm considering taking all new boots there now before I've even worn them. I've certainly caught heels a few times with the new shanks that would have taken the original heels straight off but they didn't even come loose. The place I go to is K G Shoes near Mornington Crescent Tube Station. Very strongly recommended if you need leather repairs in London.