There are a few places abbreviated to L B on various censuses:

L B Hackney (London / Middlesex) = Lea Bridge Road, Hackney
L B Deverill (Wiltshire) = Longbridge Deverill
L B Manchester (Lancashire), not figured out what that one means yet
L B Burn (Durham) = Low Beech Burn
L B (Northumberland) = Longbenton
also as has already been mentioned.
L B (Bedfordshire) = Leighton Buzzard