Hi Danielle,

First off all, welcome to Flyertalk! What a shame you had to go through this. It is certainly not the norm! This is from own experience.
The staff in LHR was probably contract, so that could have played a roll.

What I do find odd is that you arrived with only 1:10h to spare. If I remember correctly, when you have booked assistance, you will have to be present at the airport quite early. So if you could check if this was mentioned when you booked the service?
Still, it should have been enough to make the flight.

As for the return, I am sure that will go smoothly.