A few random thoughts (with the caveat that it was outside UK):
1) I think it's better to start first with a good training provider (one that's up-to-date on current national and European laic resuscitation guidelines) and follow up on that with online info than the other way around. There is just too much potentially confusing or outdated information on the internet, and the training will help you differentiate. Of course, that does not apply to online info from trusted providers, like mentioned above.
2) Perhaps the best outdoor first aid training I remember was a several days long, very immersive one, with surprise simulations after any theory and again much longer ones later (I hated that random 2AM wake-up call), bivouacing outside in the winter (a safe location with facilities nearby, just plenty of cold and snow). I do believe any well-done training that takes you right to or slightly over the comfort limit is the most memorable...
Of course, that might be out of scope of simpler first aid training for beginners, but still, the more immersive, the better.
3) Later, perhaps considering volunteering as a simulated casualty with your local MRT for their own training (if they need volunteers). It does help them and it might help the volunteer as well. And of course rehash your training every once and then.
Any pros, please correct me if I have it wrong
Post edited at 12:19