1m,
It is pretty difficult to help when you won't tell us anything else except thet you are pissed off and you're going to get them. What is the exact nature of your complaint against CMC, and how do you intend to prove that any contract was breached?
If, for example, you had evidence that CMC were exercising your instructions based on conditions different to other clients (i.e. they singled you out in order that a Stop was breached), then you might have something. Still, I doubt very much that even if you had any evidence to show this, it would be admissible in court.
If your complaint, like most other complaints against SB firms, is that the price of the contract they were quoting (and you were trading) differed from the "underlying" enough for unexpected profits/losses to be incurred, then I'd advise you to say goodbye to the cash and save on litigation.
While it clearly frustrates you that, in your opinion, you have been mistreated by CMC, I will make a few points that you should consider before you go hunting for a scalp:
(All the following is based on the assumption you were Spread Betting rather than CFD trading; there is a big difference between these two contracts, but I honestly doubt any difference in the result of any legal actions you may undertake).
* By entering into a SB agreement, you accepted that the value of your payout would be determined by CMC. Yes, they sell their services (the provision of risk) by giving the impression that prices of the underlying will behave in a similar manner to some well publicised index etc... - however, in your T&C's you can be sure that CMC will have made a stipulation that prices may differ - Unless they have grossly abused the trust of their clients, your case will fall apart here I should think.
** Moving on from that, if I were instructed by CMC to defend them... (Which, I hasten to add i have not, nor am likely to be, nor would accept such an invitation anyway... you never can be too careful what you write on these bloody forums, even a joke offends some!)... I would do a regression on the "real" index vs, the price CMC were quoting. I expect you would find the two were very closely correlated, so any argument that they were grossly misleading you fails here. The fact that CMC know where to diverge a little doesn't matter (this would be were the SB / CFD argument differs, as a CFD will have some exchange listed underlying i think...).
*** Given that you've got a judge to accept the first two points, you still have to prove that CMC moved prices against you illegally. CMC will openly admit that they manipulate prices - they will say that, as part of good practice, they have limits on their risk. Once a certain level of risk has been met, or *in the view of their risk professional / head dealer / whatever*, CMC were overexposed - and, being the good and honest set of people they are, they changed the prices they were willing to deal at in order to reduce the flow of incoming risk, in order that they be able to meet their existing agreements. I guess this is the manipulation you are talking about?? Of course it's manipulation, but there is nothing (legally, at least), wrong with it. In dealing with CMC, the "market" you were trading was not the "true" index, but a combination of some underlying and the "market" of CMC customers. CMC will have told you this in some round about way before they accepted your deals.
**** You have mentioned that in the past you have "punished" CMC by quoting inefficient prices. By this I assume you mean make a profit, i which case you must suck it up. What goes around, comes around.
***** Given the size of figures you state, it would have taken more than one instance of this to bring about the losses you claim (or an act of Darwinian stupidity). At any time you were unsatisfied with the service CMC were providing, you could have moved. You were not obliged to deal with CMC if you didn't want to, and this will prove to be a difficult point to manoever around. In most contracts there is a "honeymoon" period where deals can be "annulled", but it sounds like your deals with CMC would have long outlasted such a period.
****** Although CMC are FSA regulated, I don't think SB's come under the FSA's jurisdiction (probably for the CFD part, that's it). For tax they are regarded as a bet, it doesn't make sense that you would be able to keep the profits tax free when you win, but run to a publicly funded body when things go wrong. You could try the ombudsman though.
******* The reality of the situation is that, in order to have a case, you will need to prove that CMC changed the price of a variable they were quoting by enough so as to warrant misleading you, frequently enough to show that it was intentional, and solely to make a profit from their clients. Even if you manage this, I doubt you'll get your money back, CMC will get a slap on the wrist. They will have written a contract that Houdini couldn't get out of, and, unfortunately, cases like this are only ever won by the guy with the biggest wallet, which in all liklihood isn't you.
Your only probable hope of getting something is to make enough noise that the FSA look at changing the nature of Spreadbetting. However little it may please you, the money is gone. Legal action is only going to cause you more hassle, time and effort - let alone more money, which suffice to say, you should take better care of.
p.s. I will add that i have no legal qualifications or formal education, and this should only be considered as my opinion, not as legal advice. Given that I've written all that, I believe I am entitled to remind you that Peter Cruddas is not the Messiah, he's a very naughty boy. In this case, Grant, I think crucifying him would be a little over the top (even if it's his first offence).