Re: How long the data is held.
It's called "running interference". Eventually the punter will give up, because it's not worth it. One reason to use one of those companies that do it for you. The good ones will have taken Halifax all the way to bailiffs at the head office wanting to distrain their goods, and Halifax will be paying up rather more readily. Having said that, the banks hate those companies and want to make life hell for them too. Another factor is the correct calculation of interest charges. If at any time since, you became overdrawn, but wouldn't have done if your account balance at the time had been correct, that's also a consequent loss they owe you, with 8% interest ever since. The difference between what they give you voluntarily, and what you can get by carefully analysing the financial consequences ever since the PPI can be huge. Very frequently they are unable to produce the document you originally signed, or they only scanned the signature page, so they have no basis in court to justify the money they took at all.
Of course no rational person ever signed up for PPI in the first place, so it's all academic.