An update (see my post above)
So, I requested the Terms and Conditions from Tesco showing that gambling is treated as a cash advance... they swore to high heaven that they were correct (in saying that gambling was mentioned as a special case in the T&Cs),... despite the fact that I had their T&Cs in my hand and was quoting from them, and they didn't have access to their own T&Cs, which is quite incredible.
They claimed to have posted the T&Cs to me on three to four occasions, including by Registered Post,.. however I never received any of the letters, although I have received over 5 years of statements with no problems. (There was a postal strike in the UK though in late 2009, to be fair.. but I still received all statements though)
Eventually they accepted that they were wrong, that their customer sevice was wrong, that the supervisors were wrong, and that they had no right to treat gambling transactions any differently, and that the Irish T&Cs didn't mention gambling. I insisted that they write to me when they had decided how to correct this issue and the overcharging.
So nothing happened for four to six weeks, ... so I rang them... they said all refunds had been issued... so I pointed out that mine hadn't.. they said they couldn't see any refunds due on their system, until I read from my statement of Sept 2009, clearly showing a cash advance interest charge... so they retracted, and then said that yes, I was due a refund (of 50c, it's not the money...).. . but they also claimed that my situation was unique, a one off, and that all other refunds had been processed correctly. I asked what evidence they had for that... they had none... except the dubious evidence that one customer sevice Rep had not heard of this issue and didn't receive any calls about it. So Tesco assume that everything is fine unless customers are complaining, so they're clearly re-active rather than pro-active.
I told them I had lost confidence in their ability to correctly administer my account and charges, and asked why should I have confidence in their systems given this acknowledged failure and Tesco's poor response and dismissive attitude. They seem to be ignoring this issue.
Do people feel I should report the matter to the Finincial Regulator??
... quite simply I don't believe Tesco when they say they have processed all refunds, I don't believe them when they say they have issued letters to all those affected, and I have actually, genuinely, lost confidence in their professionalism and their ability to correctly and fairly apply charges. Prior to this I had considered Tesco Finance to be a very professional company, and I am actually shocked at their dismissive attitude to what I see as a serious problem.
Cheers