I was recently wondering why I can only get 45mbps while my line works at its full potential after DLM reset even tho the cabinet which I am connected to is 2 roads away (not too sure it is my cabinet but I noticed PCP box with number 14 painted on it just 15 metres away from the FTTC cabinet. As far as I know the PCP box can't be farer than 50 metres away from FTTC one. Note that the BT checker says I am connected to cabinet 14 on Stanley exchange so knowing that PCP can't be farer than 50m from FTTC cab, this is most likely the cabinet I am connected to.
Using your images, I agree that you appear to be connected to PCP 14, and this appears to be sited on Stalisfield Avenue, here:
https://goo.gl/maps/9JTwjb4LgAzIt certainly *says* it is cab 14.
The FTTC cabinet itself appears to be on the junction of Elkstone and Clanfield, here:
https://goo.gl/maps/fFbWaRWowWG2Using Google's own distance measuring tool, the FTTC cabinet appears to be 58m away from the PCP (BT allows up to 100m, but prefers less than 50m); this distance will need to be included in the length of your line, as the VDSL2 signal will be attenuating across all that distance to PCP 14, and then back again. And that distance on the tie-pairs will allow for some impact from crosstalk too.
Then checked the distance between my house and the FTTC cabinet using google maps (I know bad method 
) and it gives me distance around 400-450 metres, and according to VDSL2 (FTTC) Speed vs. Distance graph, I should be getting attainable of approx 70mbps.
The distance measuring tool estimates a total of 570m, if you start from the FTTC cabinet and run to the PCP, with the copper then returning from the PCP via Clanfield back to you, or 590m if it runs via Swallowhurst. The minimum appears to be just over 500m if it runs via Marshfield and the footpath - if BT routed that way.
TBB's own speed-vs-distance estimations (admittedly pessimistic) would have you down for 35-38Mbps at those distances.
Distance, of course, isn't everything. Thinner copper can result in the performance of a longer, standard gauge, line. As would aluminium in place of copper. But it is much harder to judge whether those apply.
My attenuation is 22.8 dB (used to be 22.0 dB last year).
This is a much better measure to use to figure out performance than raw distance. However, I don't think we've managed to put together a decent "attenuation vs distance" or even "attenuation vs speed" table.
When you look at other lines on MDWS with a similar attenuation, there seem to be a lot of lines with speeds in the 40's. A couple in the 60's admittedly, but most are in the 40's.
There is quiet few Clanfield Roads (where the closest FTTC and PCP are), no mention of the other further away cabinet.
Unfortunately, Codelook make a guess about the road name in those tables. It uses a part of the postcode - the centroid, the geographic centre of the postcode - and works out which road is closest. It will be right in some cases, and wrong in others.
Once you have clicked on the cabinet link (eg P14), then the map shows you all the postcodes served by that cab. For P14, it certainly looks like your street is well and truly part of P14. The other cab you considered looks to be P20; the map of all its postcodes seems to include areas north of your street.
