There are several things which can cause uneven tyre wear. The biggest culprit, as you rightly say, is poor wheel alignment. If the front wheels are toed in too far, they tyres will generally wear on the outside edges. This can also be a result of enthusiastic cornering! If the front wheels are toed out the tyres will wear on their inside edges. Generally speaking, if tyres which have been subjected to an uneven wear pattern on the front, are then moved to the rear, where wear SHOULD be more even across the tyre, the wear will not "even up", but continue as it has begun, but evenly, if you follow.
However, that is not the full story. Some vehicles have fully adjustable front AND rear alignment which must be set, on a laser jig, to the manufacturers spec. I don't know if the Focus (and by default the C-Max) falls into this category as I have not had mine long enough to find things like that out.
Tyres which are under or over inflated will also wear unevenly. Under inflated on the outside. Over inflated in a ring around the centre of the tread. If a tyre which has been subjected to overloading on the rear axle is then moved to a poorly aligned front axle it is a recipe for uneven wear. However, as I don't know you, or your driving habits, I cannot say exactly what may be causing the uneven tyre wear. I am just making you aware of the pitfalls.
So, as you can see, there are many things which may be causing your problem. The first thing to check is your tyre pressures. Also, are you in the habit of occasionally carrying heavy loads? Unless you change the tyre pressures to cope with the extra load, it could cause "under inflation" problems to start.
If you are concerned that wheel alignment may be the cause of your problems, a full four wheel alignment check at a reputable specialist will get it sorted or at least set your mind at rest. If the alignment is correct, it can only be down to inflation, loading and driving style.
2008 2.0 TDCi Zetec