It is worth pointing out that in most places the Freeview signal isn't currently strong enough to make internal aerials viable. Do remember that the strength of the analogue signal is MANY times the strength of the digital and it'll stay that way until the analogue signal is turned off.
As an example our nearest transmitter is the Waltham one. It currently transmits Freeview at an ERP (effective radiated power) of 4,500W. On 1/5/2011 (switchover day for here) that signal strength will be increased to 37,500W.
If you can wait then I would advise you to do so as you will probably have to upgrade any Freeview box you buy now anyway (for HD/MPEG4 broadcasts).
Edit - apparently Waltham currently transmits at 7,300W and has done since last summer, which correlates with a fairly dramatic improvement to the reception on the ITV mux here. Shame 99% of the programming on the ITV mux is junk but you can't have everything