Personally I wouldn't go for it. It is cheap...but:
Basic Aluminium frame will be pretty heavy.
Built up with very basic kit.
Running 35mm tyres on a heavy basic bike I don't think it will be much more rideable than your MTB with locked out forks and slicks on it.
If you can spend some more money as it will more than repay. If you can go to £750 then the difference in bike will be far greater than the comparative difference in the price.
I'm a big fan of do everything touring bikes and think steel would be better as it would be more comfortable and durable than the heavy aluminium and wouldn't weigh anymore, probably less. My GB frame is only cheap far eastern steel but very comfortable and was £250 including fork, so not bank breaking (don't know if you can still get them, if not then the Aeron alu frame is the same price and better than the one you link to - not sure about the tyres it will accept and not steel but...).
A proper touring frame will take 28mm tyres and some up to 32mm tyres if you want a wider tyre for feeling of stability, but you can always shrink them down as you want, or not as the case may be.
9 or 10 speed with a compact as you can then have a far wider range of options open to you for upgrades or just plain replacements when worn out.
Another option is something like the Uncle John from Planet-X that Aodan rides. Great do everything bikes, I think Aodan's done everything from touring, through MTB rides to racing at Palace on his
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[quote="Dombo"]Do you really need all the racks and stuff? I'd have thought a pure road machine would be better.
A touring bike is a pure road machine but unless you are using it as your "race" bike then it is far more sensible to have braze-ons for mudguards and a rack. You can take them off whenever you want for a stripped down bike but have a far more versitile machine for everything else. Everyone used to have a does everything bike and race on them without any problems, not having mudguards in the wet and winter just gets you and your bike covered in cack, the bike components don't last as long, and you're more likely to get cold and catch something.