My mathbe off but it sounds like this guy bounced about a hundred checks.
I think this discussion is missing a significant point in the story. That is, the bank was not forced to pay the money back to him because the charges were ruled improper. The judgement was against them because they refused to even respond to his claims, thus abdicating their legal rights.
It seems to me a bank can pretty much charge you what they like (legally) as long as it is made clear up front what these charges are going to be and the customer enters the relationship with a clear understanding of these charges. I don't think they are fair or reasonable charges, but if one takes the account with full knowledge of the potential charges, well, I can't see any illegality here.
As far as this guy's figures, he may very well have computed interest and damages into the amount for which he was suing.
Over the course of six years, this is not especially outrageous for a small retailer. Commercial accounts are also charged when a customer's check bounces. The shop no longer operates, so I can guess it was a small concern and sometimes had cash flow problems. In a couple of slow weeks, with the bank piling it on for overdrafts and other fees, they can generate a nice revenue stream for themselves at the customer's expense. I don't know why the man went out of business, but 3400 pounds in fees had to hurt.