Fibre: Slow Speeds - Modem Replaced

[#1]

Had Fibre for 12 months or so.  Stopped paying attention to speeds after the first 3 months or so, was constistantly around the 35 mbps, and ping of 5 secs (using Speedtest.net).
On the Extra + Pro package.
My modem was replaced by Plusnet a few weeks ago (part of their bulk replacement thingy as modems were found to potentially be faulty).  Been tracking speeds since and seem to get 20-25mbps and 25ms pings. 
Can I have my old modem back!!?
Any thoughts?

[#2]

Has your IP Profile also reduced?
The BT Speed Test will show your IP Profile, but apparently the actual speed tests are sometimes inaccurate recently.

[#3]

No, profile is fine.  37mb.
Gateway hopped yesterday.  And still had below par results, but today shows 5ms ping and 30mb download.  Better.. getting there.. Hadn't expected fibre on the Pro package to have such variance in permformance.

[#4]

Hi Discord,
Is the result via ethernet or wireless? Have you tried running one directly from the modem?
Jojo