Yes, BT have a demarcation point which is normally the managed router - what you plug into is up to you. Some providers will provide a managed firewall / UTM appliance to secure the private network but that normally has an additional monthly fee.
Back in the OPs original thread, there was information that a device to set between the ISP router and private LAN were needed (eg posts 9 and 10).
If needs be, ring up a firewall vendor like (Dell) SonicWall, Watchguard, Checkpoint or Junpier (to name but a few) and get their sales to tell you who your local reseller is. It's a bread & butter requirement IMHO.
Back in the OPs original thread, there was information that a device to set between the ISP router and private LAN were needed (eg posts 9 and 10).
If needs be, ring up a firewall vendor like (Dell) SonicWall, Watchguard, Checkpoint or Junpier (to name but a few) and get their sales to tell you who your local reseller is. It's a bread & butter requirement IMHO.