Thinking of taking my lad to London for a few days, week after next - do some site-seeing.

I have 2 options:
> Drive and stay somewhere (with cheap/free parking) on the outskirts, but with a tube station into town (e.g. Watford)
> Train into St Pancras and stay central

Happy with basic-ish accommodation as long as it's safe, clean and has a TV.

Any suggestions?