Hadn't looked at the sig speedtest - in general they are historic and irrelevant. Yours isn't
The upload is consistent with that seen on Openreach GEA 10Mbps sync and BT Wholesale 10,000kbps upstream IP Profile. I suggest there is some reason for that 2Mbps drop between sync and throughput which applies also to your setup. (My downstream thoughts following may also be relevant to the upstream).
When you say it goes to the BT Cab and from there to the Thales cab, do you mean the BT Cab is an Openreach FTTC one, or the original PCP?
If it is an Openreach FTTC one then I expect the feed is you >> PCP >> FTTC DSLAM, (as normal), >> Thales cab.
If so, the Openreach DLM will be running on the DSLAM, with a maximum IP Profile of 38717kbps, before the handover to Thales. On the common BT Wholesale that generally gives 36-37.5Mbps throughput, depending on the standard of the ISP's backhaul, routers and so on.
So again, as with the upload, I wouldn't see an issue.
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