You could sent MBNA something like this (edited to suit):
I refer to the above matter and your failure to supply ldocuments (or whatever the alleged failure is) in response to my s78 Consumer Credit Act Request or to provide a true copy of a properly executed credit card agreement.
We appear to be at odds in this matter, and clearly you remain in default of the Consumer Credit Act 1974 on this matter.
The original properly executed credit card agreement is the document that you would need to produce in support of any county court action against me and the same document that I would make a court application for you to produce if you failed to respond to such a request under Civil Procedure Rules prior to my seeking to commence proceedings against yourselves.
It would therefore seem to me to be entirely in line with the overriding principles of the CPR for us to make every attempt to settle matters outside the court.
In furtherance of this objective therefore, I would suggest that this matter can be disposed of without further delay by you allowing me to inspect the original properly executed credit card agreement. Thus the matter can be resolved one way or the other.
I can think of no valid reason, if it is your sincere desire to have this matter dealt with without further delay, why you should not accede to this request. Since clearly if you satisfy me that you do have a properly executed and enforceable agreement then I can immediately enter into discussions with you with regard to discharging the said debt, which is surely what you are trying to achieve!
If however it is the case that you do not possess a legible properly executed agreement then it would be better for all concerned for you to admit to this fact now and then we may be able to negotiate a mutually acceptable outcome.
I would remind you that whilst this account is in dispute you are constrained by s78(6) of the Act as to what enforcement action you may pursue, which includes the issue of default notices demanding payment. You should consider this letter as a reminder notice under section 10 of the Data Protection Act (1998) to cease processing, with immediate effect, any data in relation to this account, both within your own internal records and records with any third party agencies, that may cause substantial damage or substantial distress to me or to another.
To sum up, I am not obliged to make any further payments to you until you provide me with a copy of a properly executed agreement. Should you not have a properly executed agreement in relation to this alleged debt, please confirm this in writing to me. If you do have a properly executed agreement there is no reason why you should not allow me sight of it in order to resolve this dispute.
I would appreciate your due diligence in this matter and I look forward to your reply in the first instance but definitely within 14 days from receipt of this letter.