You may want to correct your LHR description:

LHR - EXCEPT T5 GATE 15 (Stand 515) where there is no facility to repatriate you with a pushchair or wheelchair. If a person's own wheelchair is desperately required, it may be brought up to the corridor by Gate 13, but that is the exception rather than the rule.

Whilst on the subject, if you have got a stroller for Return to Door, you may as well relax on the aeroplane and take your time getting your stuff together. It usually takes at least 5 minutes, and often closer to 10, from the aircraft being chocked before your stroller will appear. I'll tell you why........

1. Aircraft comes on to stand, engines power down. Loaders plug in ground power cable and chock wheels.
2. Airbridge (sometimes called jetty or finger) is attached, loaders place cones to draw vehicle drivers attention to wing and engine extremities to prevent damage.
3. First Passengers are already disembarking. Loaders are operating cargo hatch doors and bringing "televator" (the machine that moves containers) and conveyor to the aircraft.

3a. If "Dry Ice" (Carbon Dioxide in solid form) has been present in the hold (Perishable Cargo is often packed in Dry Ice), then the loaders must wait for at least 5 minutes before entering the hold. Dry Ice removes oxygen from the atmosphere and there is a risk of suffocation if the hold is entered too early.

4. Pushchairs are finally brought to the building.