Made the move......................

[#1]

I have just made the application for the switch from Extra to Unlimited as the profile of the service is better and the the money saved is welcome
Just for the record here is what RouterStats has to report 'now' 22:22 hours on the 5th Feb
Shows a consistently good sync for I think the longest number of days I can recall. 
So all being well the switch will happen with the Static IP address maintained and the sync & stability equally so 
DL
Noise Margin:    2.1  dB
Connection Rate:  3913  Kbps
Line Attenuation: 55.0  dB
Power:            0.0  dBm
Max Rate:        4524  Kbps

SuperFrames:      311744523
SF (CRC) Errors:  36985
Reed Solomon:    3395269344
RS Corrected:    1417930638
RS Un-Corrected:  496807
HEC:              31449
Errored Seconds:  21826
Severe ES:        81
Interleave Depth: 32
Bitswaps:        1558242

ULNoise Margin:    6.0  dB
Connection Rate:  820  Kbps
Line Attenuation: 28.4  dB
Power:            12.9  dBm
Max Rate:        828  Kbps

SuperFrames:      252645060
SF (CRC) Errors:  1
Reed Solomon:    4294109
RS Corrected:    21
RS Un-Corrected:  0
HEC:              0
Errored Seconds:  1
Severe ES:        0
Interleave Depth: 4
Bitswaps:        67977
UptimeTotal Uptimes (From SF counts):
WAN:  61 days, 08:08:29
LAN:  61 days, 08:08:29


CRC:  36985
LOS:  1
LOF:  0
ES :  21826

BT speedtester (best of 3 re-runs)
DL 3.23
UL 0.68
Ping 86.63
IP 3.45Mbps
PlusNet Stable rate = 3.4Mbps

[#2]

When the product change takes place in the early hours (3-4am) of your billing date only your service profile needs to change. This involves just the PPP connection to Plusnet dropping and reconnecting, no need to re-sync, so your sync speed shouldn't be affected at all.

[#3]

Thanks for the added insight
So just(?) a PPP session drop and reconnect  
Edit ~ just need to keep an eye on a closed ticket???

[#4]

Yes, it was just a PPP drop and reconnect when I changed.
You should have one closed service notice/ticket now which confirms the product change instruction. On billing date, in addition to the normal tickets several more will appear, one of which IIRC changes you from monthly billing to monthly billing (but it keeps the system happy).

[#5]

I know not to relevent to the upgrade and more likely to do with the Gateway issue and PlusNet "work" this morning but after nigh on 64days the WAN was dropped by the exchange and resync'ed slightly lower for the same margin 'level'   Though the differnce is very small it has taken me closer to the point where the IP could drop down a notch but hopefully not?
Routerstats information
DL
Noise Margin:    3.0  dB
Connection Rate:  3876  Kbps
Line Attenuation: 55.0  dB
Power:            0.0  dBm
Max Rate:        4980  Kbps

SuperFrames:      22369
SF (CRC) Errors:  2
Reed Solomon:    1454016
RS Corrected:    20033
RS Un-Corrected:  61
HEC:              2
Errored Seconds:  22665
Severe ES:        85
Interleave Depth: 32
Bitswaps:        20
UL
Noise Margin:    5.9  dB
Connection Rate:  828  Kbps
Line Attenuation: 28.4  dB
Power:            12.9  dBm
Max Rate:        824  Kbps

SuperFrames:      21398
SF (CRC) Errors:  4
Reed Solomon:    167548
RS Corrected:    15
RS Un-Corrected:  0
HEC:              2
Errored Seconds:  4
Severe ES:        0
Interleave Depth: 2
Bitswaps:        0
Uptime
Total Uptimes (From SF counts):
WAN:  0 days, 00:07:23
LAN:  63 days, 23:06:03


CRC:  39020
LOS:  2
LOF:  9
ES :  22666

[#6]

Plusnet work on the gateways should only cause a PPP drop, not re-sync. BT engineering work in the exchange is the more likely explanation. Or your router just felt like it.
It looks like you are on 21CN so IP Profiles don't change in 500kbps steps.

[#7]

Yup, on 21CN so within the limits then ~ phew 
So more a co-incidence in regard to the re-sync happening on the same morning as work on the Gateways.  But as you perhaps the PPP session dropping made the router take a powder 

[#8]

Update
This transition from Extra to Unlimited went through a short while ago and as indicated by spraxyt there was no obvious impact on the connection ~ as far as I can tell including in RouterStats not even the PPP session was dropped, the sync and Margin are the same and the static IP is unchanged.
Having said all that, what I have noticed is that the browsing is for want on another word "snappier", granted we are now 2am so maybe there is less congestion and other factors that one might expect to slow things down at times but under Extra I do not recall the browsing being so rapid for page/site changes and page refreshes ~ so if that keeps up that would be an added benefit 
FWIW I could discern no such user experience benefit when I changed from Premier Option 1 to Extra???

[#9]

Glad to hear you're happy after the change Routefinder

[#10]

Quote from: _Adam_Walker_

Glad to hear you're happy after the change...

Hi Adam
So far so good and the apparent page loadings etc is good and still (relatively) snappy