Then the people who pay for those licences should have been shouting DECADES ago, and it's entirely their problem to sort out. There is nothing I, as a consumer, can possibly do about perfectly legitimately-sold devices interfering on radio bands - I do not have and can not have an FCC / CE-style analysis of my devices done on a whim and then modify those devices based on their output characteristics.
Those people paying for those licenses should STOP, explain WHY, and/or SUE. Until they do, nothing will change. Until they do, nobody (in general) will know there's a problem. Until they do, people will KEEP BUYING these things totally legally and using them, totally legally.
But if there's NOT a law stopping it, or a guarantee enforcing clear bands, then there is NOTHING that *I* or *THEY* can do about it. The way forward is, was and always has been to get some legislation to stop those devices being sold. They're not doing it, they're not doing it effectively and it's arguable that they *CAN* do it at all now (too damn late for a start!).
This is not a problem I can solve. I can name 20 people with PL kit who rely it on for their home networks (e.g. where wireless won't penetrate). I can't name one that knows it's a problem for radio hams, nor one that would care so long as it was still legal to use/buy the device (and it is!).
This is a problem that licence holders should have analysed, reported, and had action taken back in the 60's or 70's. There's no difference between PL kit and any other in respect to the certifications it passes or anything else, and thus it's always been possible to do this kind of thing.
I have no sympathy for license-holders that pay for exclusive use of a certain band and HAVE NO WAY to enforce that band, and won't stop paying, and won't sue (or were silly enough to take a licence that doesn't give them a way to sue if it's not fulfilled), and won't threaten withdrawal. And, from what I see, it's not actually those licence holders who are most complaining, it's amateurs.
If this is a problem, those people affected need to do something about it.
If this was a big problem, those people would have done that and solved it decades ago.
Meanwhile, every second those devices are on general public availability, it will take longer and be harder to get rid of them (literally on the order of decades).
I can't emphasise it enough - penalising the USERS of those devices is nonsensical. You have to target the manufacturers and those certifying the devices. And there, there's NOTHING I can do to help you, everything should have been done YEARS ago, and you should have moulded a watchdog that works in your interest (I don't think allowing low-level FM transmitters in cars, etc. was in radio hams' interests either, but you let it go through). There is nothing the average consumer can do for you, and they will continue to buy these devices and make the problem worse. Not least, because they work wonderfully well and don't interfere with ANYTHING that I can detect or use in my average day.
Again, if the hams have a problem, they should have done something about it long ago, or they should at the very least do it now - but the amateur licence is stupidly cheap and comes with no guarantees and the larger users *aren't* complaining and if they are, they certainly aren't suing or fighting for refunds on their licences.
I cannot help you. The manufacturer's are pushing out firmware that does help you (thus acknowledging the problem) but nobody can force me to use it. Someone needs to take Ofcom, or the manufacturers, to court and get these things banned if they are that much of a problem. And if you can't get that far, or can't do it, or lose in court, then I'm perfectly happy to carry on using such devices as they will have been confirmed "legal".
Too little, too late, with too little proof of too little impact, and too little interest in doing anything about it.