No, I was stationed in England for 3 years and it's true that they had detection vans, though I never saw one. Rather than have commercials you had to buy a license and I always kept mine current.
In addition to the BBC, there was an independent channel that did have commercials.
The shows on BB-1 and BBC-2 didn't necessarily start and end on the half hour. A show might start at 7:17 and end at 8:42. You really needed a guide to know what was playing. One annoying thing was that a show you wanted to watch might end on BBC-1 at 8:42 but a show that you also wanted to watch might start on BBC-2 at 8:23.
A little off tangent but I watched a couple episodes of Monty Python’s Flying Circus on Netflix over the weekend. Thanks to the citizens of the UK for financing it!