The "clearing house" question is quite interesting.
The EU position is that the majority of EU denominated derivatives (mostly interest rate swaps) should be cleared within the EU and the clearer should be oversighted by an EU based regulator (they've suggested the ECB).
There are a couple of problems with that:
- Japan tried the same thing different reasons. What resulted was a vast, offshore "dark pool" of yen (for both FX and derivatives) that had more liquidity than the local market. The reason for the higher liquidity is that offshore clearing houses provide netting facilities, whereby asset and liability positions are netted, irrespective of their nature (so long as they are deemed eligible assets by the clearing house and regulator). Thus, a bank with derivative (or cash) positions in multiple currencies across multiple asset classes only needs to deal with the credit position arising from a single, netted, position in the currency of their choice. The result is that clearing yen offshore is cheaper than clearing yen onshore in Japan. For swaps, it's quite a significant number. For the EU as a whole, it would be a very significant cost to EU businesses, putting them at a further disadvantage; and
- the EU simply does not have the regulatory competence to oversight clearing. Strange though that may sound, it's true. The most capable is BaFin (German regulator), and yet the global lead regulator for Deutsche Bank is the UK FCA (as an SEC imposed settlement requirement arising from their frequent breaches of AML law and lack of supervisory competence).
There is nothing the EU can do to prohibit UK based firms clearing Euro denominated positions, as evidenced by the Japanese experience. There is, however, a good deal the the UK can do (and, possibly, should do) to restrict EU based banks accessing clearing (i.e. apply greated supervisory oversight than EU MS domestic regulators currently apply, particularly as it relates to solvency (itself a subset of credit risk)).