Outside of bike parks and trail centres, almost all the media you'll see of people riding in the UK are riding on "unauthorised trails". As an example, the area I live in is on the bottom edge of what's known as "The Valleys", and as you'd expect it means there's a lot of prime hillside to be digging in. This area also has a lot of forestry managed by Natural Resources Wales (NRW) who are effectively the stewards of the outdoors in Wales. Within a 20-30min ride from my front door I could get to 7-8 different spots (I believe the fashionable term is "zones"?), all created and and maintained by different groups, none of which has authorisation to be there. These vary from rut tracks through to bike park style runs that are arguably better than the actual bike parks near me. In the rest of the UK it does vary a lot simply because the geology of the UK is very different from one area to the next - we have short, steep, tight, tech rooty trails for the most part here, whereas if you went to the Lake District it's bigger mountains with longer trails that are all fairly rocky. There's everything in-between.
There is definitely tension between different user groups, but I think most long-lasting trails tend to be built with those in mind, and typically won't feature high speed crossing of walking paths, will usually be a bit more tucked away and so on. NRW only really seem to step in when people build actual wooden features on trails, which was something that became a lot more common in lockdown. I think there's generally an acceptance from NRW and their equivalent body in England to generally turn a blind eye to trails, but if things start getting obviously constructed/built then they step in as I think the concern about liability if someone fucks themselves on a shonky pallet ladder bridge goes up. I believe Scotland has a different setup as they have a totally different setup as far as land usage goes to the rest of Great Britain. Scotland has what's called the "Right to Roam" which means:
"Landowners are under an obligation to ensure that the public are able to exercise their right to roam over the land that they own and are prohibited from obstructing or discouraging others from exercising their right to access. They must use and manage their land in a responsible way, having regard to the rights of the public."
I think for that reason there tends to be more of a push for legal or authorised trails up there - it seems that way from down here, anyway, as they have more trail associations and more trail advocacy going on up there compared to down here. In my local area, felling work by NRW has threatened a lot of spots so a few of the local digging groups have become more 'official' to work with NRW and the logging companies to try and carry out works in a way that minimises damage to the trail networks. Tourism is still a pretty big thing down here, and they actively use mountain biking as an advertising tool, so I think it's in their interests to not totally fuck the trails. They even legalised an unauthorised trail network about 20mins from me that came to light when the main digger there crashed and died while riding them. Everyone thought they'd shut them down, but they ended up coming to an agreement with the dig group there and made it into an 'official' spot. It's in this video from about the mid-point onward when it gets a bit more bike parky. The trails before that are all unauthorised ones.
As for riding wet trails, that's just the reality here. We get rain on average just over 1 in every 3 days throughout the year, so if we waited for the trails to dry out we'd probably get about one 3 week window to ride per year. It means that more maintenance is required and overall there will be more erosion, but that's just the way it is. It's the same way footpaths and walking tracks tend to be a bit more manicured in most places here than I've found elsewhere on my travels, simply because use + shit weather = more work required.
