Is this normal ?

After my connection has been connected for several days, the downstream SNR will rise by 1db or sometimes higher,

In the past it has held at this upper level for days, but then dropped back to the normal level again,

Also my upstream SNR continually fluctuates and has done since my current connection went live,the level of fluctuation which currently isn't so bad 0.5db up/down from target ,

But in the recent past has been as much as 1db + any ideas as to why it does this,

Yes very normal.

I would say that 1dB is not really normal ... most lines fluctuate by 3-5 dB and even as much as 7dB.