Long LHR layover

Is the layover during the day, or an overnight one?
Is it on one ticket (so your bags are checked through) or on two tickets?
That would assist people to give a helpful response.
If you leave the airport a lot of that time will be taken up with passing the border and then going back through security.

In the past, rates at the T4 Premier Inn have been extremely reasonable. You might check on www.premierinn.com . The hotel is a bit of a walk from the terminal, but it's through a connected, covered walkway.

Our flight arrives at about 0730 from JNB Terminal 5 and we depart for Canada at 1720 from Terminal 3Our bags will be checked. Not really sure how much time we will have if have to thru customs and security if we leave LHR….

The tiny Yotel room spaces were barely bigger than a pod, but are no longer in the airport. And there are luxury lounges, where you might be able to buy day access for a high price. Last time I had a long layover, I just got an orange plastic chair, and waited it out.

So basically, you are not changing time zones very much (if at all) on the way but you will have been up and flying all night. I would consider simply renting a room at a moderate priced hotel and sleeping. Plaza Premium Lounge at Heathrow runs about 42 a person. So $84 will get you a place to hang out but not really rest.

I have not personally used this site, but I find it an interesting possibility for finding dayrooms.
https://www.dayuse.co.uk/

Thanks for the Dayuse site. Looks like can’t book more than about 4m out but will be a great option to explore. If anyone else has used this site please tell us how it went.

There used to be sleep lounges (pods) in Terminal 3 but sadly they are closed.

Dayuse is probably your best bet. If not, and you want to stay at the airport,,

What airlines are you flying?

There used to be sleep lounges (pods) in Terminal 3 but sadly they are closed.

Dayuse is probably your best bet. If not, and you want to stay at the airport,,

What airlines are you flying?

And in what class on the plane? Economy, Business?

We are flying British Airways. And unfortunately economy. BA lounge entry requires business or first. Lounge 1 is closed. I think our best bet is to try for a day use hotel room..

The No. 1 lounge (
Club Aspire) at Heathrow T3 is open. The only problem is they only allow a three hour visit. However, they do allow you to purchase extra hours. I'm just not sure if that is only if your flight is delayed.

The sleeping pods are closed.

https://no1lounges.com/airport-lounges/heathrow/terminal-3/club-aspire#:~:text=All%20passengers%20travelling%20through%20Heathrow,airline%20or%20ticket%20travel%20class.

If all goes to plan with the first flight you should have time for a short visit to Windsor if that appeals. You could have a look round and have some lunch before getting back to LHR. Whilst it’s possible to do the journey by bus it’s an easy 20 minute taxi ride.

can you buy your way into the BA club or use credit card leverage or such? there's also a chain of clubs called Priority Pass

No you can’t. You can only get into the BA lounges with a Business or First ticket or with BA status at Silver or above or the equivalent with a One World partner.

I would encourage you to go for the day room. You have two very long flights and two nights without sleep. I would find a way to sleep on that day if you can.