We are going in August for the first time so I will see soon if what we're doing is really worthy of a recommendation.
It all started when I read about somone getting RT flights for $475 pp from Boston, amazingly cheap! We live around 10 miles from Philly but we felt the savings would be worth the drive. Before committing, I did keep checking fares from JFK and Newark, NJ in hopes of getting something a bit closer, eventually settling for $619 pp from Philly on Delta.
I found a very nice Marriott next to the London Eye, across the river from Big Ben. It's not cheap but it was recently remodeled and location seems perfect.
For tours we are using The English Bus for a small group tour to Stonehenge & Bath.
Then for our city tour of London we opted for a private 7 hr tour with London Magical Tours. I chose them not just for their good reviews on TA but also because they offer a driver and a guide, so the guide can take us to every attraction without have to deal with parking the car.
This doesn't leave us much free, leisure time because we're only in London for 3 nts before flying to Paris for a few nights there, then on to DLP.
I really wanted to take the Eurostar train (Chunnel) to Paris just for the experience but after reading about tips to reduce the odds of being affected by a terrorist such as not using public transportation, it got me thinking that I'd rather just fly. I know that may sound irrational and of course real odds are less than miniscule but I have to follow my gut. Flights were cheap, like 67 euro pp including luggage and choosing seats, so it's cheaper and faster.
I don't know if this is any help but just thought I'd share what we came up with.
Have fun planning!