So I spoke with C&J NYC today. Their resoling service costs $210, has no tax and includes shipping back and forth to the UK. Boots will be resoled on the original lasts and you can choose any sole you want. Sounds great to me, so I think I'm going to get my new (to me) dark brown Harlechs Ridgewayed!
Sweet idea. Please be sure to post pics - very curious to see how those come out.