It is largely down to the quality of the line, distance from the exchange, etc., as you surmise. In general, your speed should be very similar downstream, perhaps less upstream.
In the case of a move from TT LLU, (is that what you are on?), to Plusnet there are two factors that affect things. One is the noise margin TT have your connection set at, and the other is the BT Wholesale IP Profile system that Plusnet connections are subject two.
The TT noise margin may be higher, so reducing the speed, but they don't have IP Profiling which can. Even that is a simplification however, as the IP Profiling system accounts for (absobs) some of the overheads of the connection whereas the TT system loses throughput by not having it.
Are you able to see your router stats? Connection/sync speed, attenuation and noise margin/SNRM? If so, please post them.
Which exchange is it please? This is important, as it affects everything above.
The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
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