So let me see - airline pilots complain when GA pilots use 121.5 for practice (among other uses). I bet they also complain when they're re-vectored because some low-time PPL has blundered into the controlled airspace they're just about to occupy. Which would you rather ? Or should we train PPL to ATPL standard coz then they wouldn't make nav mistakes, would they ?
80 calls a month = just short of 3 a day, for a minute. And prior to appearing on 121.5, the instructor with the stude will have asked London Info if it's ok to make the practice call.
My lowly opinion, FWIW - live with it.