Just thought I'd post this for those Linksys users who are having problems after Plusnet's upgrade process to MaxDSL where you get a DSL link light but your device states that the Interface is down. I've had this for a number of weeks now and only after one of the CSC support chaps (Mike Wheeler) spent some time and patience with me have we been able to fix it.
This is for the Linksys WAG54Gx2 but I believe the same is probably for other units. This device supports ADSL2+ and this is what BT have added to my line. The base firmware version 1.00.01, I assume switches this automatically so you will not be able to connect when you get moved to Maxdsl.
Update with the latest firmware -I used v1.00.09 for this model and carry out a hard re-boot. However, the device in my case mis diagnosed the VCI setting as 35 - switch the device to manual input and set the VPI to 0 and VCI to 38 and you should now connect.