Hi Wesley S, Eltham is in South East london and south of the Thames River - Belgravia is in West London (North of the Thames) the two are probably only 20 miles apart but if you're driving it's not the easiest of journeys and you should expect to be held up in heavy traffic for most of the journey! probably best to take public transport.

PS: if you're coming straight from Texas best make an early start if you want to get a floor spot!

Best Wishes
Tony