I don't "know" the answer to your question. However, the CTR requires you to break down debits and credits to cash by "location."
If you click on Item 35, State (critical field), the only things listed on the drop down are U.S. states and APO/FPO (military locations). If you click on item 37, Country (critical field), the drop down list only shows the U.S. and what appears to be nine U.S. territories and protectorates of one stripe or another.
So, if your customer withdraws cash in your London office, I don't think you are required to report it because it would basically be impossible.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.