UK Financial Sector - why so secretive?

I've been trying to put some hard numbers on the scale of Financial Transactions in the UK, and my latest estimate puts the number at over £2 quadrillion for 2014. But it's hard work finding the information. One of the reasons is that for some reason, the UK Financial Sector doesn't seem to want to live in the same world as everyone else.

For example, there is a thing called the World Federation of Exchanges, which is "the trade association of 64 publicly regulated stock, futures and options exchanges." In fact, their web site includes information about no less than 192 different structures. 110 are full members of the WFE and there are a further 67  described as "Affiliates and Correspondants". There are just a handfull that are described as "Non Members". They include the two exchanges in the US (ELX and One Chicago), a few in various countries like Argentina (Rofex ), India (MCS-SX "India's New Stock Exchange", and the United Stock Echange of India) Iran (Teheran Stock Exchange) and Japan (Tokyo Commontity Exchange and the Tokyo Grain Exchange). Otherwise, for Europe, there are just two exchanges that are not part of the system : The Warsaw Stock Exchange, and the London Stock Exchange.

Why does the London Stock Exchange not want to be either a member, or even affiliated to the World Federation of Exchanges? Why has it also decided not to be included in the FESE (the Federation of European Securities Exchanges)? And why does it not provide any figures to the Bank for International Settlements - BIS - which has been recording "nav" (Not Available) since 2005, a year when the total value of executed securities trades was £5.2 trillion?

I've already complained about the fact that major players like LCH.Clearnet Ltd have avoided providing open information to BIS since 2009, and that level of secrecy is seen for several other players like Barclays, whose Bar-X trading platform appears to be invisible to anyone who is not a paid up member of the platform.

So, what's the explanation? 

My guess is that secrecy is one of the great strengths of the UK Financial Services industry. There have been numerous cases in recent history where it has been clear that the UK offers clients a wide range of options for hiding their financial transactions via a bewildering array of offshore sites. It's clearly a very lucrative proposition for many. But I think that this also explains why the City of London is so committed to blocking any attempt to introduce anything requiring transparency, including the option of a tax on financial transactions. Indeed, now that Cameron and Osborne are back in power for another 5 years with an absolute majority in Parliament, they are probably breathing a sigh of relief. They will now be able to count on the UK government to block any such propositions. It doesn't matter that taxing transactions make incredibly good sense for just about everyone. Keeping things hidden is clearly even more important.