To try to clear this all up a bit there are two basic ways of viewing/recording the off airs (BBC1, BBC2 etc.) on 1-5 on your TV
1. A bypass, these are fitted internally on some of the older Digi STBs and externally on the newer ones, afaik the analogue STB's are all external. (though I'm sure some one can probably prove me wrong
)
The bypass uses the analogue off airs provided by the cable company so an aerial is not needed.
I've been assured that there are bypass's available for all Langley Digi STB variants with exception of the Samsungs (which don't count yet anyway) as I posted earlier.
2. An aerial Combiner, these are all fitted externally on Langley Digi STB's but internally on Bromley STB's and require you to have a serviceable aerial on your roof, top of TV etc. for you to get your off airs. They are also available for all Scientific Atlanta brand analogue STB's. Not sure about the GI analogue STBs.
In short then;
Langley digital, both bypasses and combiners available,
no aerial needed.
Bromley digital, no bypasses available so an aerial
is needed.
Analogue, bypasses and combiners available for SA STB's
probably for the GI STBs as well. There may be some regional variations though and cust services
should be able to give you an answer for your region.
hth