I admit we are outliers here, but we always use the Heathrow Express to and from Heathrow.
We are in our late 70’s, fully mobile, but I detest the Tube, especially with luggage. We tried that once, just to get from our apartment on the South Bank to Paddington for the HEX. and it did not go well—-the mornings trains were too crowded to board with luggage, and we had to let 2 go by before we realized we had to walk to the farthest car, which is supposed to be less crowded, and then just grit our teeth and force our way on. After that 2016 experience, we said No More Tube with luggage.
We buy our tickets for the HEx 90+days in advance so they only cost £5.50 each. If we are not staying near Paddington (which we rarely do) we walk outside from the HEx platforms (which are at street level) to the taxi stand and take a black cab from there to our hotel. Total cost from airport to hotel door is usually right around £30 for the two of us.
I do not understand the comment above about what a long walk it is from Terminal 5 to the “Heathrow Express Station”, because the platform for the HEx trains is right IN Terminal 5, on a lower level accessed by large elevators. According to the Heathrow Terminal 5 interactive map, it is a 2-minute walk from the arrivals area (just after baggage claim and exiting past customs) to the elevator down to Level -3, and a one-minute walk from there to the platform. Total distance 164 m.
https://www.heathrowexpress.com/visitor-information/heathrow-airport-information/terminal-maps/terminal-5#/
The OP needs to get to T3 but I assume there is a similar arrangement (tho we’ve never doe it from there). The Heathrow website will answer the question if they are curious.
On our most recent trip,this past September, we flew into Heathrow from Venice on Sept. 19 (the day of the Queen’s funeral) and the HEx and Elizabeth Lines were not running because of a fire in the overhead wires somewhere. So we had to take the Tube, or pay some unknown price for a taxi from the ranks. We chose the Tube, despite our earlier vow, because by this time, near the end of our trip, we had already incurred so many unexpected extra expenses due to various cancellations and last-minute bookings that we just wanted the cheaper option. It was a miserable journey.
The Piccadilly Line originates at Heathrow, so one boarding there faces no huge crowds already on the train, and has a chance of getting a seat. We did, but by the time the train had gone 3 stops it was so full, and the aisles so packed, that people trying to get off had trouble getting to the exit door in time. We knew we had to change trains at Earl’s Court to reach Paddington, so we started moving toward the exit doors two stops early to make sure we could succeed. But then we realized we were blocking others so we just got off at Hammersmith, thinking we could just take the Circle Line or H&C to Paddington, but for some reason that did not work—the line was out of service or something. So we got back on the next Piccadilly Line train ( slightly less crowded) and rode that to Earl’s Court to change to the District Line to Paddington. And finally arrived there an hour and fifteen. Minutes after leaving Heathrow.
I am not trying to talk the OP into taking the HEx, just saying that Piccadilly line is not a good option for them. But if they are still interested in the Heathrow Express,I suggest they (a) buy the tickets online well in advance for the best price, and (b) take a cab from their hotel door to Paddington.
