Ok, I'll admit I'm an Anglophile, so London is one of my favourite subjects.

I agree with those who recommended the double-decker buses, for a start, Double-deckers are a London trademark, and for anyone not already familiar with this city, it makes by far the best introduction to the classic landmarks. I don't know what they charge today, at a guess 15 pounds, but that gives you 24 hours of transport around the circuit, which compares more than favourably with tube and bus fares, not to mention cabs. They have two or three different circuits (not transferrable) so you could fill two or three days that way.

My favouirite is the red bus, rather than the gold & maroon or any other coloured operator, though I have no evidence to support that preference.

They all 'start' at the top of Hyde Park's Eastern end, just near Speakers corner, though you can pick one up at any designated stop, and these are in lots of central places, such as Haymarket, Aldwych, etc.

The weather in March should be OK - probably no more snow, likely lots of light rain (which can be at any time) but not terribly cold. I have even had some warm days in Marck over the years.

If you want my tip - get on one of these tours early in your stay, it will make the task of understanding London a lot easier.

Paul in Sydney