Edinburgh to Heathrow and then to Nashville

Have you already booked flights? If not could you look into open jaw flights arriving in perhaps.Edinburgh and home from London or the other way around. It would save back tracking.

"Everyone who boards a new flight will have to go through Security" is how LHR's website phrases it.
My experience is that even though you went through security in Edinburgh, you will have to collect your luggage and run the gauntlet with it at LHR before it will be loaded onto your plane returning home. I would be concerned that 2 hours 5 minutes may not be sufficient time to accomplish that as LHR is a very large airport with a lot of walking involved and any unforeseen delay-- the weather, a heightened security issue for LHR, a flight delay at Edinburgh--any could trip up your timing. Gail's advice above is a good plan.

all on one ticket your luggage will be checked through from Edinburgh to the US. You won't collect it at Heathrow.

The only customs you encounter will be entering the US. 2.5 hours is fine.

Ramblin'On, The OP says the connection is 2 hours five minutes, not 2.5 hours. However, BA says if both flights have the same reference number and are on the same ticket you will not need to collect the luggage at LHR. You need to be at the gate at least 20 minutes before your flight. If BA booked these flights for the passengers, then BA is obligated to see they get to their
final destination.

Where does the Heathrow website say that RR’s statement is wrong? It is correct. For flights booked on one ticket, bags will be checked through from Edinburgh to Nashville.

When I work through the “flight connections” for this transfer on a random date in the future, it doesn’t even show a new security check in T5. I presume that is because the first flight originated within the UK, and their security meets Heathrow standards.

It also says that the minimum connect time is 60 minutes and they are well beyond that.

Maybe this will come through, but maybe not.

https://www.heathrow.com/connecting-flights/flight-details?flightIds=BA1441,BA223&flightDate=2023-01-09

Edit: I see that Kenko has revised their response to acknowledge that RR is correct.

Lola, Heathrow.com/connecting flights under "Why do I have to go through security again when changing flights."
Cheers!

Back to the OPs original question. You don't encounter Customs at either Edinburgh or LHR on your return flight. You won't have that until you land in the US. If your flights home are on a single ticket, then your luggage will be checked through to your final destination.

You will have to clear security in both Edinburgh, and LHR ( because your flight is departing to the US). As long as your first flight arrives on time, and hopefully leaves from the same terminal, you should be ok.

I flew Edinburgh to LHR to BNA (Nashville) on August 8 on a single British Airways ticket. This is how it worked:

Edinburgh
-I had checked in online the day before and already had boarding passes for both flights
- I had only carry on luggage but opted to stand in line at the BA desk to have my passport checked there...just to be on the safe side. Maybe I could have skipped that and had my passport checked at the gate.

-There is no step of "clearing customs."

-I went through security.
-At the gate, I heard an announcement that the flight was full. Because I was in the last boarding class, I chose to gate check my rollaboard with the gate agent because I knew overhead space would already be full by the time I boarded. She tagged it all the way to BNA, and I didn't see it again until I arrived at BNA.
-Note: be sure to arrive at the Edinburgh airport plenty early, at least 2.5 hours. I departed Edinburgh at 8:00 a.m. I arrived at the terminal at 5:30 a.m., and there weren't that many people waiting to check in at the British Airways desk (which seemed understaffed). However, soon afterwards the line waiting to check luggage quickly backed up when a bus arrived, and once past the BA desk, the security line was long.

Heathrow
-Arrived at Terminal 5 and departed from Terminal 5.
- Because I had already cleared security at another UK airport, I did not need to go through security again.
-I followed the signs for Connecting flight-Terminal 5 and walked right into the huge departure lounge.
-I carefully watched the departures board, then once the flight to BNA gate was announced with "proceed to gate." I immediately proceeded to the gate

Nashville
-Deplane at the far end of the terminal because must go through immigration (passport control). Luggage carousel is right there.

Regarding your question about whether a 2 hr. 5 min. layover at Heathrow is sufficient, my view is that it should be IF you are flying into Terminal 5 and departing from Terminal 5 and IF your flight from Edinburgh is on time. However, if I were in your shoes and could change to an earlier flight from Edinburgh, I would. When I flew on Aug. 8, Heathrow was just recovering from operational issues and I'd already had my EDI-LHR flight cancelled once (a month before the flight). I opted to depart Edinburgh at 8;00 a.m. and had a 5 hour layover....boring but not stressful. Heathrow seems to have settled down since August. If I were flying now, I would still prefer more than a 2 hr. 5 min. layover.

I apologize for the accidentally huge font at the end of my previous reply!

That’s OK. That can happen when you paste something from another source.

So you did not go through security again at Heathrow T5? That confirms my impression from working through the “flight connections” planner in the website, for a flight coming from Edinburgh. The security at Edinburgh meets “UK standards”.

Flying from Edinburgh to Heathrow to Nashville on a single British Airways ticket in August 2022: .I went through security in Edinburgh but did NOT go through it again at Heathrow.