You are one of a handful in the UK using this method I suspect. First I've seen post to our forums.
Fortunately have used ADSL where PPPoE is more common.
Which ISP, generally PPPoA and all the details being set in the router is the preferred method?
Do have a good read before doing anything, and if unsure come back to us with questions.
At point c - the router auto detects the best connection type, dont worry too much what it picks, just enter the username and password the ISP gave you.
For VPI use 0
For VCI use 38
For encapsulation if it detected PPPoA earlier select VC-MUX
If it found PPPoE use PPPoE LLC
The VPI/VCI may vary, as a few providers in the UK use different ones. If you browse around the router screens you might find out what the current ones are.
By doing PPPoA or PPPoE in the router you should get a more stable service.
Follow the instructions that are for Mac and Linux users (and windows users where CD will not run)