There is only 1 cobbler I use, and that's George's at Finchley road tube station. George is the owner. An old guy who's been running the place forever. He knows exactly what to do. He's vibramed every pair of CCP and Augusta shoes/boots I've owned (including sneakers). Ask for him and only leave your boots with him. Worth calling in advance to check he's in....he'll want at least a day as he won't rush them.
Remind him exactly what you want (in terms of not touching the sole etc and balancing the sole) and you can sleep well knowing he won't fuck them up. He'll probably mention he looks after another guy (me) with the exact same instructions 😉