Long layover at Heathrow

Could you offer any advice to using the Tube for these locations and in general. Additional information,

Pay using a contactless card or device.

Get the tube map at TfL.gov.uk to get where you want to go.

Right now buy a Heathrow Express ticket. 15 minute train ride to Paddington Station. Once there use your tap debit or credit card and take a London Underground train…Circle Line to Westminster. 15 minute ride.

Mind the Gap, exit the train and take Exit 4. You’ll come out across from Elizabeth’s Tower with the Big Ben Bell. Tower looks great after nearly 3 years of cleaning and refurbishing. On the hour Big Ben will toll.

From here you could walk up Whitehall to Trafalgar Square OR follow Birdcage Walk adjacent to St James Park up to Buckingham Palace.

As you mentioned the British Museum its 20 minute bus ride from Westminster Parliament Square Stop C to Tottenham Court Station. Then a 10 minute walk to the Museum. Its the 24 bus. Sit up top for best views.

Now clue about luggage storage at Heathrow. You’ll need to research. https://www.left-baggage.co.uk/en/locations/left-luggage-heathrow-airport

Can't answer your airport questions but here's a thought if you can't leave bags at the airport ... book a room at one of the nearby hotels, hopefully with a free shuttle ... there are several close by (but might be cost-prohibitive) ... after deplaning and going through immigration/customs, go to the hotel, check-in, drop your bags then go back to the terminal and catch a train into London ... you should have most of the day in London ... then go back to the airport and hotel for a shower and maybe a short nap ... don't know the terminal you depart from so you might need to catch a taxi back to another terminal.

AA is in Terminal 3. It stopped operating out of Terminal 5 months ago. They do not fly between London and South Africa. More than likely it's a British Airways flight. Look at your ticket. It will say who "operates" your flight. If it is British Airways, they are in Terminal 5.

I stand corrected, I forgot they moved ... my previous post has been updated.

On arrival you will need to go through passport control. If the E gates are operating it should be a fairly quick process. But it all depends on the passenger load when you arrive.

Your options for transportation between heathrow and London would include

• Piccadilly line (tube)
• Elizabeth line
• Heathrow Express
• National Express bus
• Taxi/minicab/Uber

Tube probably the cheapest and the car based options the most expensive. The 3 train options offer frequent service. Heathrow express can be expensive if you don’t buy tickets well in advance.

Showers appear to be all in the lounges. If you don’t have access through some type of membership or airline status you can buy a day pass.

https://www.heathrow.com/at-the-airport/terminal-facilities/toilets-and-showers

Edit. There’s a left luggage facility at T3 just after you leave secure area of arrivals

There is an excellent chance that you will not need to reclaim your suitcases and they can be checked straight to CPT from South Africa. My experience has been that if the layover is less than 24 hours at Heathrow and I can check straight through.

You won't have any big time changes to deal with, but you will have been up all night. How well do you sleep on flights?

You simply enter the UK through passport control. This has gone fairly quickly for me the last few times with the egates. Then follow signs to either the train or the tube.

Upon return you go through security and back to airside. The Plaza Premium Lounge has showers. There may be an additional charge beyond the day pass to the lounge.
https://www.plazapremiumlounge.com/en-uk/find/americas-europe/united-kingdom/london/london-heathrow-airport/plaza-premium-lounge-departures-terminal-5

Heathrow Express is NOT the best option to Westminster, now you have missed the cheap tickets by many weeks (the booking window is now 5 months). Even if those were available it is 15 minutes into Paddington main line station, then transfer to the underground, then 17 minutes (not 15- 17 is TfL own timings) assuming a train arrives the second you arrive on the platform- at least 40 minutes.
The Elizabeth Line, changing at one of several central London locations is less than half the price and only a few minutes slower
or even Piccadilly Line to Hammersmith, changing to District Line is only 48 minutes (TfL timings, including the change), and only 1/5 the price of Heathrow Express for an easier option which is only a handful of minutes slower.
Both Elizabeth Line and the Tube are far more frequent than HEX.

"book a room at one of the nearby hotels, hopefully with a free shuttle"

Very few hotels in London have shuttles, free or otherwise.

I had a similar situation some years ago -- early morning arrival at Heathrow, early evening departure for Nairobi. My day in London went well. Took the regular Tube to a station near Bloomsbury, walked around, had a good visit to the British Museum when it opened, lunch in a pub, walked around some more, then Tube back to the airport in plenty of time to go back through security and catch flight. My luggage was checked through and I either left my carry on in a left luggage or carried it around with me, don't remember. Looks like you'll have even more time with a departure to Africa not until 10:25.