Not really sure why they decided to look at London. What the Hell's in London related to crypto? Article author assumes wherever legacy finance is, Bitcoin's bound to go? I don't mean to say London doesn't have a significant number of bitcoin users, but the last time I read a BTC-related press release out of London was, ummm..... never, and considering favorable legislation and a strong user base already exists in the stronger economy of Germany, looking at London as some kind of "capital" seems left-field.

How exactly is the value of a bit coin decided?

It is not so much that they don't want to see large withdrawals to coinbase it is that they do not like to see a lot of withdrawals to coinbase and then a large deposit from coinbase. This makes it look like you are conducting business out of your personal account (which you are) and it looks like you are potentially check kiting via ACH transfers.