I think what I was confused most about was why it had seemingly gone to debt collectors but was now back to Anglian Water sending me the bill again. As it's been explained, they supposedly sell the debt on to a debt collector - assumingly at a lower amount - and then the debt collector goes on to retrieve the full amount from the client so that they make a profit. However, if that was the case and the debt collection agencies had bought the debt, surely they haven't sent ONE letter and decided to sell it on to yet another debt collection agency? And then that debt collection agency send ONE letter and sell it back to Anglian Water?? To me it seems most likely that Anglian Water contact a couple of agencies and tell them whoever gets me to pay the money back then gets a commission from it but when they get no response after 1 letter, they decide whatever commission they're going to get from £80 is not worth the time and energy of doing anything more and they pass it back to AW who then go about trying to get the money from me themselves again.
But this is the thing - I don't know what's right anymore. If one piece of information is being given out and doesn't seem to add up then it makes me ask where the information is coming from in the first place? I mean, I heard of Veronica Chapman sending a letter to a debt collection agency saying, "Thanks for paying my debt, now it no longer exists" or something like. But that can't be true. Or maybe it's just in some cases...I don't know. And the problem is I can't find this information out by just searching the internet - you kind of have to have insider information to find out first hand you know?
I'm sorry to sound doubtful, but I don't want to be one of those people who just believes whatever someone tells them without doing any research myself or asking questions. Look where the world is because of people doing just that! So yeah, I'm just trying to equip myself with all the knowledge on the subject that I can. Knowledge is power as they say

. And if you're going to put yourself in the line of fire, you better have something to back you up and know what you're talking about, right?