I'd be very
surprised if your neighbour gets 76Mb at 800m from the cabinet.
That's full sync. Many can't get that at half the distance.
Sounds like your neighbour is quoting their package speed.
Can you post the estimates from the BTw Broadband Availability Checker
Also, where are you getting the figures for your line? From the modem stats or from a speed test?
Can I get something done about it
If you are below the estimates then maybe.
If you are within the estimates for your line then no.
Just because your neighbours get higher speeds doesn't mean you can.
Crosstalk is a random lottery. Interference from a neighbouring line can take as much as (maybe even more) 20Mb off your current sync speed.
Different modems can perform better than others. Different DSL patch cables perform better than others.
A new DSL patch cable gave me a 4Mb increase in sync. Swapping modems has got me another 4-5Mb.
DLM can also play a huge part in sync speed.
If you are a new line on a Huawei cabinet then your line is likely interleaved. This takes roughly 10% off your sync.
If that's the case, by the time DLM applies G.INP and reduces the target SNRM to 3dB your sync could climb from 45Mb to about 60-65Mb.