Well, I have to admit that I was looking for some combination tool for some time too.
Not the Rambo Bowieknife, but something to cut, slice, carve, saw and chop with. It does not exist. At least not in the quality that you can really cut, slice, carve, saw and chop, keep your tool intact and keep all of your fingers.
So, settle for more than one tool and take with you what you need for each job.
I usually have a SAK with me al all times. I have a Victorinox Rucksack (the third know is 10 years) Its a bit larger than most folders and it locks so I guess that would make it illegal in Britain (I live in Holland). When outdoors, on a hiking trip I usually go with friends. So we can share equipment and add some luxury to the bare essentials. Bare essentials of course are some kind of decent knife for everyone, SAKs or Opinels seem to be favorite, a Mora is more sturdy of course but a knife on your belt is a bit of trouble when carrying a large pack. The luxury of course consist of some vintage single malt, but also of my machete and a hand chain saw. Thats great kit. It cuts like nothing ive seen before and if you have top you can take down quite large trees as it is two feet long. I prefer it highly above a folding saw, but of course you could differ on that.
The machete is I thing a bit in dispute for junior bushcrafters and I have to agree. Its lethal, realy. Thats when its sharp. When its blunt its maiming, but probably even more dangerous as you glance a lot more. I think you should learn the chopping business with an ax, thats a bit less of a killer and easier to handle. Learn it at home or in your garden, tot somewhere in the bush with no one around!