Water Bill question

nowtsevereasy

We lived for 4 years under a Housing Assoc in a flat that had no meter and the water bill was levied by a department of the HA. 
Each year I recived a letter from the HA stating the Water Charges for that year. 
I have recently transferd to another property, same HA but this one has a water meter. Welsh Water increased my direct debit payment to almost double. Upon quering this I was informed there was a outstanding amount from my time at the other property that the HA had passed onto Welsh Water.
Contacting the HA they confirmed this was correct. I had been paying on a payment card what I assumed to be the correct amount but as I had recived nothing in a statment form each year I (wrongly as it turned out assumed that I had paid all of the previous years charges off).
Upon contacting the HA water department and requesting a statment from them, I found out that I owed a amount that had been building up each year.

So my questions are.
1. Is it Best Practice for a HA to send out a letter (not worded as either a bill or a statment) which does not contain any arrears? 
2. Do any other utility compaines and buisnesses work like this-so I can avoid them in the future.

While I will clear the outstanding amout I'm not happy about the circumstances in which it develpoed.