My experience (your mileage may vary):
Last year, I replaced a 2012-era ADSLNation plate with an Openreach mk3 faceplate, which was the first version to include the filtering Andrew referred to. It gave me a useful extra bit of speed at higher bins on ADSL2+. I bought it from Amazon Marketplace
: about £12 or £15 with Prime.
BTW, since then, Openreach launched the mk4 version, which only works with the new, toolless design of NTE.
3 km line on THTG: 19/1.2 Mb/s with Sky
Previously: BT ISDN, Nildram, Plusnet, 186k, EFH, Be*, Plusnet (again), Pulse8