Britguy:
To all you guys who have replied with helpfull suggestions, much appreciated, and thank you for taking the time to do so.
The Chorus guy came out again today, and he did indeed find a bad line (the second fault he has found), right at the house connection. We are back up to 5Mbs at the moment, so we should be okay. I'll take a good look through the many useful suggestions later in the day, when I have the time to do them justice.
When I purchased my house and had to leave the HFC network as it was not in my area and went back to ADSL I ran a dedicated jack point and installed a master filter
one of these https://cdlnz.com/XDSL-MASTER
and the fools to install it this https://cdlnz.com/A-UR-3100 and this https://cdlnz.com/CT-105
all for less than $50
the reason I did this even though I had Naked ADSL with BigPipe the previous person had POTS on the line, so if you plugged a phone in you would get disconnected beeps
If you connection is naked, try plug a phone in and if you get the disconnected beeps you DEFINITELY need a master filter, you may even get more than the 5Mbps you are getting now
I am now on Fibre now but for the two years I was on ADSL I am glad I made this simple investment