From the list of bikes you gave the Trek is not designed to go touring unless you're only going to be credit carding it, the bike has no mounts for panniers only fender mounts. The Triban, as is with the Trek and others some mentioned, the frame is aluminum which unless it's very high end aluminum like the Koga you might suffer from reliability of the frame when touring, not to mention a harsher ride vs the steel bikes and on long rides you don't want to get beat up riding. So in my mind that only leaves the Planet X and the
Ribble, the Planet X bubbles to the top only because it has the capability to use 32c tires vs only 28c max size on the Ribble, and if you'll be doing in touring you'll want to use 32c tires. Thus from those four you showed the winner is the Planet X Kaffenback.
One poster mentioned the Trek 520, it is a very good touring bike and is a bit more stout then the Planet X but it also weighs about 10 pounds more then the Planet X, so since you mentioned you wanted to do lighter touring and not full on expedition touring then the Planet X wins again.
The mentioned Genesis Equilibrium has lower end Tiagra, though not a bad group by any means, but the Rival 11 on the Planet X is one step up from that. In addition to that the Genesis uses a carbon fiber fork which I wouldn't trust a no name generic CF fork made in China to hold up for long and especially for touring. And of course we have the same problem with the Spa Cycles bike when it comes to the fork; plus with the Spa the bike uses a standard frame instead of sloping top tube, nothing wrong with that but it does make it a bit more difficult to dismount when loaded.
However the other Spa all steel tourer bike
https://www.spacycles.co.uk/m1b0s21p2983/SPA-CYCLES-Steel-Tourer isn't bad, actually I might like it better than the Planet X. The Sora shifters are only so so vs the Rival 11, but you can always upgrade those when they fail. Also the Spa uses better Reynolds 725 and steel fork with eyelets for pannier rack and fenders as well as a third set of water cage mounts which is very important for touring. Plus it comes with Tubus racks and SKS mudguards. I would NOT go with the upgrade TI rack, TI in that diameter is not strong enough, plus the rack when made correctly can actually help control a loaded bike and TI is too flexy to do that job adequately. I think we have a winner...unless the weight of that bike which stands at around 28 pounds vs around 23 pounds for the Planet X is a put off. The weight issue really depends on how much weight do you EVER foresee yourself carrying when touring, the 28 pound bike is due to a beefer frame and fork like the Trek 520 has, but if you will never be doing any long term touring and thus have no plans on carrying a great deal of weight to support yourself for longer periods of times then the Planet X is fine, but if you want to cover your bases in case you do then the Spa steel tourer bike is the one to get.
Now there is one other bike to consider, though this one will cost more, but if you plan on keeping it for a long time and do long distance touring in all sorts of weather then this next bike you should seriously consider even if that means waiting a bit to save up more money, and that's the Kona Sutra with disk brakes, see:
http://www.konaworld.com/sutra.cfm that bike notice that it's shifters are on the ends of the handlebar, that's for better control when shifting a loaded bike, and it keeps the bike simple, plus in case you crash and damage the brake lever you're also not damaging a more expensive brake with shifter. Also the Kona has a better gear range for climbing steep grades on a touring bike, the front has a 26 vs a 28 small ring gear, and the rear has a 34 vs a 32; not a big deal because you can always change gears rather cheaply but this bike is ready to go; but the Spa uses a road bike front derailleur instead of a mountain bike derailleur like the Kona does, so to get the Spa to use a smaller chain ring you might also have to change out the front derailleur but again those are not expensive. Of course the Kona is more expensive but you do get a lot for the money including better all weather brakes, better tires, better seat, better gearing, better crank set, more reliable and less damage prone shifting system, larger 40c (vs 32c) tires for more types of surface conditions, and it's about 2 or 3 pounds lighter.
So basically the decision comes down to money, doesn't it always?! If you want to stay below $1,000 then go with the Spa Cycles steel tourer, if you can wait and save up a tad more money then the Kona is the best one. The Kona is so good you can't even find a better touring bike till you get into something twice the money and then it will only be maybe 10% better.
