I've just bought a full-size spare for my wife's 2013 Fiesta and am looking at jack options. I see from Microcat that the 'half-scissor' jack used on Fiestas for the past 20+ years but from 2012-on have moved to a 'full-scissor' type. Ebay is full of the former (for both Fiesta and Focus) but not so many of the latter and so I was wondering if either can be used i.e. is it perhaps just a result of rationalisation of parts across other ranges (I suspect the larger Fords have always have the full-scissor type) or has the seam weld of the jacking point changed in some way? If either will suffice presumably the 19mm wheel nut size has remained the same?

Just to follow this up I decided to try a jack from a Mk 4/5 Fiesta given that they are widely available on eBay and hence very cheap (<£10 all-in):

It fits fine, and performs well (at least as well as any scissor jack anyway!). The wrench is also the right size (19mm) but the towing eye is very different (the Mk 7.5 is much longer) so I'll dump that.

I would think the difference is due to the increase weight of the car. Might be worth checking the safe weight of the jack you've purchased to be on the safe side. 

Yes, you're likely right as the full scissor version seems to be pretty much the standard on larger models (and vans). This one will be fine for the Fiesta given how light it is.