I have chunky calves and cankles and have struggled for years with boots digging in and having to fasten on the widest setting. I have on numerous occasions returned boots after doing a couple of runs with boots I though were ok but had me hobbling after an hour or so. Last year I invested in my own boots with inners which were heat moulded to fit me perfectly. The first time i used them it was amazing to just not think about my boots at all, they were so comfortable. Best 200 euros I've ever spent.
I have used a heel lift (or folded ski socks if desperate) to lift calf out of the boots far enough for comfort as the racing boots were not a lady fit! I invested in another more comfy less racy pair - Found a ski shop that kitted out the paralympic team who were great and seemed to understand I still wanted performance from the boots whilst retaining circulation. It was near Uxbridge - no idea if its still there.
Bartlett's is the name of the place you're thinning off, not sure if they're still open, have a little google. Are you close Sevenoaks? What about trying Captains Cabin. Or if in London try surefoot or does the resort you're going to have Surefoot, I'm a huge advocate of them.