Here in the U.K. we had a TV channel 1 right up until the closure of our old 405-line service in 1985. The main transmitters on ch. 1 were Crystal Palace (London), Redruth (far southwest of England), and Divis (Northern Ireland), although many other low-power relays (transposers) also used it in other parts of the country.
Channel 1 was still using the same frequencies as the original pre-war BBC service: Video carrier on 45.0MHz, sound on 41.5MHz. It was certainly much more susceptible to interference, although all the VHF "Band I" channels (1 through 5, extending up to about 67MHz) could get hit by signals from Continental Europe when conditions were right. The hot summer of 1976 provided many instances of such interference during the long summer evenings.
It was quite common during the 1970s for the BBC to put up announcements between programs telling people "Do not adjust your sets." As Independent TV used only the "Band III" channels (starting at ch. 6 from about 174Mhz upward), it was generally less affected than the BBC.
It was the same over here. I took in CB repairs for several years, but one of the reasons I dropped CB work in the end was that I was getting more and more fed up with (a) getting nowhere trying to correct the horrendous misconceptions that were around, and (b) having to put right sets in which every darned preset and coil had been interfered with before somebody decided it needed repair and brought it to me.
One incident sticks in my mind of a guy who had me fit a crystal I.F. filter in his set. It improved the receiver's selectivity no end, but unfortunately, he wasn't at all happy. Apparently all his buddies had the modulation on their transmitters cranked up so far that with his improved receiver they now sounded terrible (and keep in mind that the British CB service uses FM). There was just no way I could convince him that the filter was doing its job exactly as intended and that he should tell his friends who were splattering over about three channels either side to get their deviation with limits.
I wouldn't even like to guess at how many sets came in with the calibration pot on the meter turned up to maximum by somebody who actually thought he had increased his RF output that way. Even when a transmitter did have the output tuned up a little higher, you were on a losing battle trying to convince most of them that going from 4 to 5 watts carrier power isn't going to make a huge difference and that raising the antenna or replacing the coax with something less lossly would have a far greater effect, not to mention improving reception as well.
-Paul