Line speeds (Openreach & Plusnet) + Banding?

[#1]

Hi,
Yesterday I had a BT Openreach engineer visit my home and he run some tests connected to my socket. The line speeds he was getting on his handheld device were 79.9Mbs Down & 19.9Mbs Up.
This morning I connected my Openreach modem directly into my laptop and run some speed tests and I was getting speeds close to 36Mbs Down & 19Mbs Up which I would expect as this was the package I ordered (the maximum that was available to me)
This evening I run some speed tests and I am only getting 12Mbs Down & approximately 15Mbs Up, the down speed in particular was what I was told I would get when I placed my order, this is approximately 67Mbs slower than the results the Openreach engineer was physically seeing on site.
Queries;
When I enter my phone number & post code into the PlusNet availability checker, where does this information get pulled from?
If this is a central database held/maintained by Openreach is there a chance my postcode could have the incorrect information assigned and how do I get this updated?
We are in a new build estate and other properties surrounding my street can order the 76Mbs packages which makes me think something isn't quite right.
Would it be banding that is limiting me to approximately 12Mbs, could I be tested on/switched to higher banding?

[#2]

Which product did your order ? 80/20 or 40/20

[#3]

Hi,
Thank you for replying, I ordered the 40/20 because I had no choice, similar situation on the BT website I could only order "Unlimited Faster Broadbad" not Infinity, and yet the engineer tells me my property can recieve speeds up to 79.9 Mbs?
Thanks

[#4]

Your line is syncing at the full 80/20 so I'm not sure why the estimates for the line are that low.
However the speeds still should be higher then what you were getting yesterday. Are you running these tests over a wired or wireless connection?

[#5]

Isp's get the info (sometimes incorrect) from the same source is this BT database
https://www.btwholesale.com/includes/adsl/adsl.htm?s_cid=btw_furl_adslchecker_applications_diagnosti... 
The results are only an estimate,but some isp's seem to have become over reliant on them , As you are syncing at the full 79.9mbps you should be able to change package to the one that isn't capped (40/20) the one you are on,
As for the speed test results, are the results still low during the day time, or after midnight?