Makes sense what you're saying Maxi. Do you reckon that the wheel should have worked ?
*A moot point considering that melanabb says the wheels hit the calipers*
A bit of searching reveals that the GPA and boggo 1.2 GP share the same rear wheel bearings so one would imagine that the rears would be OK, barring clearance on the brakes of course.
The fronts have a different bearing, but that will probably be different due to having to have beefier driveshafts. As Melanabb pointed out they hit the brakes so you'd need spacers really
A couple of pairs of these and those 16" wheels would be absolutely fine. Would probably need longer bolts too.
http://www.dcperformance.co.uk/cheap/424514/vauxhall/eibach-pro-spacers/s90-2-12-006.html