Not in the US and I can’t speak to the Ham licence but it might be fun to also compare Canada and the UK. We have lots of similarities. (Plus we have a few active members of this forum from Canada.)
Here in Canada, radios are licenced through Industry Canada (IC) and IC also licences the radio spectrum. Licenced users are assigned their own frequency in their licenced geographical area, in their choice of VHF or UHF. (VHF is traditionally highly used and frequencies are hard to come by, but that is changing as many businesses are going to UHF instead.)
Industry Canada does a good job with the radio spectrum, and licenced users sharing the same frequency are usually kept a minimum of 75 kilometers apart. They also assign CTCSS and DCS codes. New business users can be assigned a temporary shared frequency until their permanent frequency is assigned, and this is where we have similar shared business frequencies as you do in the UK or the US. The actual frequencies will differ, and this is why radios programmed for the US may cause interference here in Canada. Shared business frequencies still require a licence.
As for the unlicenced spectrum, we have both FRS (max .5 watt) and GMRS (max 2 watt ERP) here in Canada, and the frequencies are the same as the US. (Different than your PMR446 radios in the UK.) Radios must meet IC testing and approval, although in practical terms almost all FRS and GMRS radios meeting US FCC standards will also meet IC standards. GMRS in Canada is restricted to 2 watts power and we don’t allow repeaters but in practical terms, almost all bubble-pack radios don’t go beyond 2 watts of effective radiated power anyway, even if advertised as 5 watts.
This system is similar to your PMR446 spectrum in that no licences are required in Canada, but we use the same frequencies as FRS and GMRS in the US.
We do not allow unlicenced MURS radios in Canada. Industry Canada was studying MURS but decided to drop it entirely as there were a few large national users who were already licenced on what would become MURS frequencies, and the cost to change them would be considerable. Plus there seemed to be little demand for MURS in Canada.
We also allow unlicenced digital radios (Motorola DTR/DLR) on the 900 Mhz spectrum in Canada because they hop so rapidly that they cannot interfere with other users. They use the same spectrum as US DTR/DLR radios. You can get the same DTR radios in the UK, but they operate on the 2.4 Ghz spectrum.
So you can see that we have a mix of regulations from both UK and US. We require no licences on GMRS, much like your PMR446 radios, but we use the same radios and frequencies as the US FRS and GMRS radios. We have no MURS (and will likely never get it) but we do have licence-free Motorola DTR and DLR radios.
Marine radios are ONLY to be used by licenced operators and only while on boats or licenced shore stations. We rarely get hunters illegally using marine frequencies because most of them use FRS. Two-way radio communication during hunting is also restricted in some hunting activities in many provinces. IC takes violations of marine radios VERY seriously, as we border on three separate oceans and have many huge inland lakes.
As for people using cheap Ham radios on GMRS frequencies - nobody cares. Here in Canada the airways are not as crowded as the US, and if one finds another user on an FRS or GMRS channel, they just switch channels. There are lots of high-power radios on FRS and GMRS and many of them are used in life-saving situations such as remote area communication, avalanche control etc. where the bubble pack radios are just not good enough quality for day-to-day use. Again, nobody cares. There are far more important things to worry about in the world than who is using a 5-watt GMRS radio instead of a 2-watt bubble pack. IC will not investigate unlicenced radios on the unlicenced spectrum unless they interfere with licenced users. One rarely gets the cranky old Ham who wants to be the frequency police because kids are all texting these days and because GMRS is unlicenced anyway, there is no practical way to tell the difference between a 2-watt bubble pack radio or a 5-watt business radio programmed to GMRS frequencies. (Plus, if you live in an area where bears roam frequently and you need avalanche beacons to get to work, it appears many of us acknowledge that lives are more important than a piece of paper.) I would never counsel people to break the law and would never do it myself, but it appears lots of people do in Canada and nobody really cares. Besides, there is not much wrong with more people learning the correct usage and the advantages of two-way radio communication.