I have had 15x7 et24s on my car from a beemer, rears were fine but fronts rubbed a little after lowering 40mm.
I now have 15x7 et 13s which rub at the back but not the front after I rolled the metal lip right up and chopped out the lip on the plastic arches.
Id say since those wheels are wider go for the ET35, or just go for the cheaper 7j ET40 ones which are pretty much exact oem fitment for a MK2! Then if you like you can space them out a bit to lower the ET if the mood takes you, or go widetrack if that floats your boat!