Apparently BT's FTTC (perhaps FTTP too?) supports using slightly larger ethernet frames for PPPoE which in turn mean that you don't have to compromise on MTU as per RFC4638 (http://tools.ietf.org/html/rfc4638). Could we get client-side support for this on the 2830s on the WAN2 port and could it be used 'server-side' on the Vigor120 to allow PPPoE to PPPoA relaying using 1500 byte MTUs (assuming PPPoE device behind the 120 can chuck out these oversized frames)?

Potentially, you might combine the two for when you have two ADSL circuits on a Vigor 2830 - one via the built-in dsl modem (1500 bytes using PPPoA) and a Vigor 120 hanging off the WAN2 port (oversized PPPoE frames between 2830 and 120 resulting in full 1500 byte PPPoA).

This is interesting as I've just installed a 2750N on BT Infinity (FTTC) and when monitoring the syslog I noticed the BT kit returns the following back to the router "your MTU is set at 1492 you may experience serious issues if running the MTU at less than 1500" I can see this on the syslog when the VDSL connection initialises.

Now its working fine and I dont see why you would get "serious" issues as it will just fragment lower surely, however is there any plans to increase the MTU capacity on these routers as I tried inputting a figure of 1500 and I get a message back saying the maximum is 1492 (the default if you put nothing in the box is this)