Everything buildersmate has said on this thread is absolutely correct. Nothing illegal has happened. Employer No1, having made an initial mistake granted, has dealt with the problem they only way they now can.
The whole scenario has nothing to do with employer no 2 who shouldn't really be involved (though in practice, if they did just put the �191.06 onto your top line in their payroll software then it would sort the position so it is a possible, if technically incorrect solution).
The technically correct solution is to request a tax return and declare the earnings on it.
In practice of ocurse if you "forget" to do so the Revenue won't give two hoots about it and you'd be extraordinarily unluck y to be caught out. Even if you were you'd end up with just the �40 to pay having pled ignorance to not having declared it if you had any sense. The Revenue tax evasion peopel have better things to be doing than chasing you for �40. It's not wirth their effort as the costs of doing so would far outweigh the tax lost.