Hi neil - another good question!
If you can, work out the interest you've been charged and include that in the total. It may also be worth sending them photocopies of your statements, highlighting the charges you are disputing.
Again, it's difficult to say with timescales - you should get some sort of initial response within a couple of weeks, depending on their policy. It might be worth asking for a response by a particular date - though you do need to be reasonable! They may claim that they have an FSA waiver due to the test case - but this only applies to the bank charges test case, not the OFT guidance.
Also, be aware that if you do have to take them to the Small Claims court, you bear the cost of starting that claim. I imagine that it's unlikely that it would get that far, but make absolutely sure this is something you are prepared to do. Seek independent legal advice if you are in any way uncertain or unsure - the claim against unfair credit card charges relates specifically to the contract you entered into with them for the provision of this service, so you need to check those terms and conditions carefully.
Have any of the forum members gone through this process and succeeded in getting their money back?
You can download the OFT statement on 'Calculating fair default charges in credit card contracts' and its advice to consumers by clicking here.
You can also find out more infomation on the bank charges test case at the FSA's consumer website by clicking here.