You should make frequent use of the various Speed Testers available, such as TBB (this site) BTW, ookla etc, to have objective assessments over substantial (calendar) periods.
If you had started earlier during your BT 1 period, you could now be making informed judgements.
My daughter has switched providers twice recently, BT (1 or 2, not sure), SKY, now on BT1 around 55/20 contractual; but only marginally above my 40/10 contract - running at about 37/9 reasonably constant, hers is now about 38/10 average BUT erratic from about 25 up to 45, very similar distances etc; but distinctly different behaviour. Different FTTCs and PCPs, same exchange.
On the previous contracts/ISPs, the actual measured performances were distinctly worse than my line.
Still trying to work out why!