I came back from Portugal last week via easyJet into Luton. Straight through the automatic gates, no questions asked about the PLF. Folks with children had to see a Border Force person. I can see how that can cause issues if there's a lot of families coupled with a lack of BF officers, it would be carnage. As was seen in Heathrow.
All the other airports I've operated into, like Biggin etc, have not asked to see the PLF. All they did was ask "have you filled in the PLF?". (We have)