Wow, thanks for all the responses guys! Some good recommendations here for sure!
I had looked into the Eurostar to get to and from Paris, but I found the price to be more expensive than flying (and it's longer, I believe, though that might be rendered moot depending on how early I want to check in to Heathrow :P). One major consideration I had with flying over Eurostar was I plan on renting a car, even though we're going to return to London each night (and will pay dearly for parking I'm sure). It just seemed easier to return the car back to Heathrow.
Globaliser, that's actually a really good idea that I hadn't considered. One thing I noticed with BA is that if I pick premium economy on their 787 going to LHR, the fare for the return ticket jumps! Would be nice to fly at least one direction in premium economy would be nice, and this might let me do that without paying more to come home.
Thanks again all. You guys are helpful!