My thoughts exactly.
I'm guessing the MX5 steering arms must be a bit shorter than the Sierra ones. I've done some googling, and other people have had similar issues mating the MX5 uprights to the escort rack.
As a temporary bodge (likely to become a permanent solution knowing me!) I've added a 20mm wide bit of pipe to each end of the rack, held on with jubilee clips.
I've now got a much more sensible amount of steering travel, and no interference problems
Once the gaiters are back in place they're nicely hidden away from the prying eyes of IVA man (hopefully!).