Umm Pippa, I don't see the point in putting frosted spuds on a comheap as they don't add any worthwhile bulk to it. I did that once many moons ago in the days when we had proper frosts, 40 - 50 years back. We had sorted out a load of iffy potatoes that weren't fit even to cook up for the hens, so being a helpful little lad, put them on the heap. Along came the rats, mother blew a fuse but the family German Shepherd loved the 'sport'. A few days of frosts followed, cold enough to cap the river with ice and completely sorted out the old spuds. The compost was turned into a smelly sloppy mushy mess...........ugh!
I recall the main worry dad had with growing spuds was with late frosts, eelworm and very occasionally, blight. Don't seem to hear much about eelworm these days.
KE