IIRC Frontier uses PPPoA for ADSL; that will limit the selection of customer supplied equipment.
Admittedly I'm in a different continent but BT prefers that you use PPPoA to connect, and there's certainly no shortage of modems available. I don't think the UK is unique in this, either.
Despite BT preferring that you used PPPoA, they will quite happily let you connect with oE if you like. Is Frontier not the same?
