i'd prefer another runway for Gatwick. Heathrow is a nightmare as it is.
i think more international flights running from the smaller airports would be great.
i also think more train lines need to be built, though of course that would be a planning nightmare too...
it always annoys me when they justify fuel tax increases by saying 'we want people to use public transport' but more people are aleady using pbulic transport (trains have highest usage since 1950's!)- more capacity is needed, not just charging people more (for both rail and road travel)