Coupe ownership has now passed 2 months

Mechanicals and paintwork are either done or under control (?) so it is time to sort out the ICE. The sound quality from CDs is brilliant, I assume NOT from the original speakers, but the radio reception (from the original Clarion) is rubbish and I cannot live without my 5Live and Radio 4 LW.
I presume that an external radio aerial is a no-no on a Coupe, but I think a DAB aerial can be put on the outside of the windscreen. Has anyone experience of this, and recommendations as to unit would be greatfully received

I do not want a bolt-on addition but a complete new unit. There is a JVC unit with a USB socket for my IPod but this runs in at £300 plus fitting plus aerial; Don't mind spending the money but some advice would be useful!
Thanks in advance
Tim42