Yeah, I ended up going to London.
My 1st hiccup was parking at the train station. The parking meter only took coins (a bit old) and it wanted £7 for the day. I did not have £7 worth of coins in my pocket so ... searching about, I see the advert for RingGo. Ok, well let's see if I have a mobile signal - yes! Download the app ... (seconds ticking) installed = add my personal info, car reg, credit card, secret question and cross my fingers = Bingo! RingGo worked! I rush to the ticket machine to collect my ticket, wait in line, train arrives. Get to ticket machine, enter my info and get ticket, run to train. I glance down at ticket and realize it is "outbound" and rush back to ticket machine to get "return" ticket, rush back to train as doors close on me... ack! find the tiny button to open train praying it would and it did. Whew! (a footnote to RingGo - I've been told to turn off notifications from them as they will charge you 50p for each one - true?)
I get into Waterloo Station and it's sheer chaos. There was some mention (from a neighbor) that there was a tube to Vauxhall (which turned out to be a train line - the closest station to the Embassy - 20 minutes walk from there) I decide in my innocence that I don't have time to find a ticket machine, get a ticket to Vauxhall and find the right line soooo, I decide to walk. 45 minutes from Waterloo ... I need the exercise so off i go.
After about 25 minutes of fast paced walking, I'm getting tired. I'm watching my phone to check the time walking along the Thames and of course, you don't foresee construction and various detours along that route. I stumbled on uneven paving stones a few times and nearly got run over by traffic crossing across the road in a panic. But finally made it to the Embassy, which has a large moat. Which I guess would be pretty in some way but they were in the process of cleaning it so it was a murky mess.
There are two entrances to the Embassy. I get in the 1st line I see, which I learned after about 10 minutes of waiting, was for other nations. I'm told to go to the other line, which is for American citizens. Okay, I go there, looking for some sign that might have alerted me earlier - there was none. Still, I'm chirpy with the guard, hoping to charm her into letting me in since I'm about 15 minutes late for my appointment. She says okay and I'm in. You have to have all your belongings scanned and walk through the body scanner just like an airport. Get past that and still no signs telling you where to go. I follow everyone else and go out the initial scan building up a long walkway to the Embassy. Again, the separation of Americans and I'm told to go upstairs to the 2nd floor.
Once there you get a number and the DX courier form (which was not explained to me - but I figured it out while waiting in line). Then you begin the booth shuffle. Wait for your number to be called. Booth 27 back to booth 3 down to booth 15 etc. Eventually I'm done having signed up for the DX courier service to my home. I can't recall the price - I think about £10.
I took a slower walk back to Vauxhall and got on the train to Waterloo. Again, chaos ... I'm not a seasoned London traveler as you may have guess. Trying to find the right platform to get the fastest train is next to rocket science in my eyes. I did finally find help from a nice guard who seemed to know what she was doing but still nerve wracking. My passport came through in about 7 days ... DX was good enough to give me a 4 hour window of delivery - no problems.