It's easy to use the "subway" in London - just walk down and walk back up.

If you want a means of transit, you'd need the Underground, which is the Tube.

Terminology matters.

>>Educate yourself how to use the subway. <<

As the others say -- uh -- nope. Tube/Underground.

>>Get an EARLY start each morning and head to the most popular sights first. You will be shocked to see people standing in 90 minute lines-<<

Again, mostly not. Where did you see 90 minute queues? The main exception is the Tower of London where you would want to arrive maybe 15 minutes before opening time.

Or Westminster Abbey -- again 15-20 minutes early.

The Underground in London is very easy to use. And I've never seen 90-minute queues anywhere in London. Perhaps Madame Tussaud, but that's a bit of a tourist trap imo.

What's your budget for a flat, LeighAnne?

We recently took tween girls to Paris & London for their spring break--4 days in each city. What they enjoyed in London: the Tower, London Eye, Sherlock Holmes Museum, the V&A, half day trip to Hampton Court Palace, tea at the Orangerie. They loved Harrod's where they purchased tote bags and macarons.

You may want to take a look at the website for LondonWalks (walks.com). They offer a variety of walks within London itself as well as day trips using public transportation.

We have done many of the their walks over the years: no reservation needed, just show up at the appointed time and place.

We have not done a daytrip but going with them would ease your hesitation about using the trains and what to do when you reach your destination.

If you want to see Westminster Abbey, do consider getting the tickets in advance. We didn't in July 2015 and the lines were so long, we didn't bother waiting. We also had a long wait at Windsor Palace. But otherwise, the lines were not bad at all, anywhere we went.

If you take the Tube please make sure to have a good plan for if you're separated. This happened to us in July 2015 with our nephew (18 y.o.) and it was really scary. We were heading to the Magna Carta exhibit at the British Library and Victoria was rush-hour crowded. http://herewegoagain-england2015.blo...-and-some.html Make a good plan for this situation and reiterate it every time you use the Tube.