I had never realized that US nationals and Canadians got that grief when they got home - I thought it was reserved for foreigners trying to gain entry.
I don't think I've ever been asked anything by anyone when returning to the UK - you just hand across your passport they have a quick look (possibly a scan) and they hand it back.
I've travelled internationally maybe a dozen times in my life. I've never once had an issue on re-entering the country. In fact, I've had a grand total of two "incidents" while traveling:
1) A security agent in Amsterdam gave me some (understandable) stern looks because my passport had gone through the wash, and was very much worse for the wear.
2) In Warsaw, I misunderstood a security agent and ended up getting a large man with a gun mildly excited (which in turn got me a little excited...). Tip: If a security screener says something in a language you don't understand and waves towards your bag on the conveyor, don't just assume it means "Take your bag and and go," it might mean "Step away from the bag"
To be clear - as a Canadian, I only get hassled when returning to Canada. When entering the United States on my TN (which I do 6-10 times a year), I normally get waived on through, while about 10% of the time I get asked "Where are you working."
I don't think I've ever been asked anything by anyone when returning to the UK - you just hand across your passport they have a quick look (possibly a scan) and they hand it back.