Absolutely no idea where all the hate towards the OP is coming from.  We're talking about a debt that he doesn't legally have to pay back as per the terms of the loan when he took it out.  This isn't an angle shot, he simply isn't earning enough taxable income to trigger the repayment schedule.  I would bet that over half the people giving it the 'pay what you owe' rhetoric would con far more out of the government with very little guilt if they felt they could get away with it.

I say double-check because although there are exceptions made for gambling income, i.e. it's tax free because of the tight margins generally involved... it's not like the government are really into the idea of a good % of people finding a way not to pay their debt back.

It's nothing to do with tight margins.  The way the tax law works, you can only be taxed on something if it meets a set of criteria to be described as a 'trade' and gambling, simply doesn't qualify, because there is no proper 'business model' which generates income.

Of course you will probably think that's bollocks, because bookmakers, casinos and such share effectively the same base business model as professional poker players and sports bettors and they clearly pay tax on their gambling winnings.  But the fact is that nobody high up in HMRC simply really understands gambling as is it practiced today and definitely doesn't understand poker.  They're certainly not interested in taxing us, because if they do then unlike in the US we can start off-setting future gambling losses against any other income we make.

Has anybody actually reported this to the police?

Yes, I know, there have been a lot of posts suggesting that it has been, people hinting they may know someone who might have done so etc, but can anybody confirm they themselves have actually been into a police station, spoken to an officer, filled in all the paperwork, got a reference number* etc?  Because the number of people involved is so large, and the amount of empty rhetoric so high, that it occurs to me that everyone might be leaving it to everybody else and nobody has actually done anything.

* I've never actually been in a police station, so I'm a bit hazy on the exact procedure, but you get the idea.

Not sure where this info about not being allowed multiple accounts on Betfair comes from.  I have two accounts, and Betfair CS actually told me to set up the second one.  I had originally asked if they could divide my account into two 'wallets', but they told me that wasn't possible and to just set up another account instead.  Since then when on the phone to Betfair I have mentioned my multiple accounts several times and it has never been questioned.