I think the UK is heading the way of the US with regards to the multiple checks and un-necessary questioning tactics by security staff who get to pretend to be immigration officers.

I was questioned by staff at security screening checkpoint in VIE for a flight to LHR so I could connect/take AC to YYZ........nothing about US there.

Definitely less hassle when transiting in the Schengen zone. This is why Schengen zone countries/airlines/hubs get my money.