I've now figured this out. The GTI jets have a shorter support at the bottom of the jet cylinder compared to the non-GTI jets.
I spotted the difference in
@willni post about retrofitting them and you can see the support clearly in this pic
Compare that to my non-GTI support bracket
For now I've just removed the support bracket, but they are well supported by the front screw and now sit at the correct angle allowing the covers to be fitted and retract properly. The support does not appear to have its own part number, so I may have to get 2 complete GTI jets.