I have just done this job on my Multi (well ony one side so far, ran out of time!).
The parts I bought also came from bypartsby, the arms seem absolutely fine, and the bushes look pretty good quality, I can't believe the price, it seems far too cheap - could be a mistake on their pricing???? The arms were delivered within 24 hours as well.
The only thing I would say is that they are cheap for the arms, but other parts in general seem about the same as everywhere else so I always shop around.
Have bought quite a few parts from Euro car parts as they do free delivery and are also pretty good on price.
The arms themselves are very easy fit - much more straight forward than a Mondeo!!.
I undid the arb inners anyway as the bushes needed replacing, but yes it is easier to get the arb out of the way slightly.
The other tip I would suggest, is to do up completely the inner mountings on the wishbone to subframe before locating the outer balljoint into the strut, that way you can easily line up all the bolt holes.
I then used spring compressors to take some tension out of the strut and could easily then locate the ball joint.
Hope that helps, Tim.