Are sticking calipers a known issue?

Yes although at 215k I'm still on the originals on mine.

Rear callipers sticking is an issue with most VAG cars due to the way the handbrake mechanism works, not just the 8P cars.

You can get a rebuild kit for them, but unless your doing it yourself, the labour costs usually make it cheaper to just fit a new calliper.

No, handbrake only uses the rear callipers and has no effect on the front end.

Unusual for front callipers to sick on these, could be a damaged piston or the guide pins.

As you said, best get the car off the ground and spin wheels. Have a look and see if the pads are wearing evenly and the face of the disc is too, also could be the pads stuck in the carrier and not sliding properly.

I don't know what callipers you have on the front, but mine are ATE (widely used on BMW as well). These have combined calliper retention and slider bolts and the section of around 2cm nearest the thread is prone to attracting brake dust which bakes on with age and heat - the end result is a sticking calliper typically after braking. Mine was doing this and when I changed all the discs and pads I cleaned these pins with wire wool and very lightly greased with Castrol red rubber grease or similar brake friendly lubricant. Afterwards all was perfect. Despite having had brake work done in the past by the previous owner, my pins didn't look as if they'd ever been cleaned before.

My rears (TRW/Lucas) are the more common type where the calliper retention bolts are first removed, followed by the calliper to reveal slider pins below which can just be pulled out, cleaned and lubed, and pushed back in. As you say, these rear callipers are prone to seizing - one of mine was "iffy" so I replaced both for about £60 a piece.

My Front offside started to do this.

But, I'm not sure how the pad and disk life were affecting it.

I'd completed 102,810 miles on the original disks and pads, so they were quite well worn, I did pull the calliper off, and did the usual copper grease tricks on the slides for the pads etc, but that didnt last long.
Changed all pads/disks, 1500 miles later, the sticking has not reappeared.

K

Silicon grease on the slide pins not copper