Is there much advantage to having these installed with regard to handling to make the rear geometry different from stock?

yes.

After lowering any of my Polo's I've always had the rear geometry measured and then fitted these to adjust the rear toe and camber back to standard - made a massive difference and much less twitchy on the rear, especially in the wet.

OK, thanks for that. I will keep that in mind if I do decide to lower the breadvan.

Regards

Phil