I hope all goes well for you.
Note what I just said about what the current line speed is. Your sync x 0.882 gives the IP Profile, and the BT Performance Test confirms that. If the current line speed is still well below that, as yours was last time we checked, then you need to kick PlusNet to correct it. It is supposed to update automatically a couple of times a day, as described earlier, but the update often fails.
PlusNet limit your download speed to the "current line speed", and that should be the round hundred below the IP Profile. You were losing 400kbps when you posted the figure

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My broadband basic info/help site - www.robertos.me.uk |
Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 55.8/14.5Mbps @ 600m. -
BQM
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.