Does anyone know the standard Focus 2.0 wheel offset. what ET it should be?

Fitted some alloys from a Mondeo and they are catching the arches.

The original alloys where 16 inch fitted with 205/50/16s and never caught the arches.

The Mondeo ones are 16 inch with 205/55/16 tyres and they seem to stick out further then the original alloys?

Just need to know the offset of best offset for the Focus as the originals sat too inside the arch for my liking where as the Mondeo wheels fill the arches nicely - but catch the arches