We have a 16 channel SMATV system in the school I work for - absolutely no problem distributing any channel around it that is FTA.
We feed the system with BBC1 and 2, ITV1, C4, C5, The Hits (a very popular channel on the school dining room TV!) and BBC Radio 1 or 4 (all from Freeview boxes), Teachers TV, TV5, TVEi, Sky News, Euronews French, In-house channel 1 with DVD or Info screen, In-house channel 2 with school radio station or local radio (switched when required) on, FTA Receiver for Astra19E/Hotbird (often on some FTA sport channel or other) and another FTA Receiver Astra28E (usually on BBC News 24).
We also modulate a 'DAB' receiver back into the system (often BBC7 or similar) and also stereo school radio sound on Band 2 (inc RDS!) - both done after seeking advice from OFCOM as well as have a Band 2 aerial feed the system. All works well with a Johanson unit doing all the necessary filtering, notching, combining, etc. (I think that's the brand)
Looked into 'the law' and was told nothing to worry about - and any subscriptions would be charged 'per head' from Sky should we need them in the future.
I've installed a few similar systems in the past and never heard of any laws or licences required to do these kinds of setups apart from, again, having to pay for any subs for channels that require them.
Leigh.....