Are the symptoms of last year disease related as opposed to crawling pests? Definitely slugs, they go inside the tuber and hollow it out
Should I plant the new crop in a different area or the same area? Different area
Should I re-plant last years ones as a laugh and see if they reproduce? No , use fresh certified seed from a garden centre.
Any other advice? Unless you have a big garden, just grow one or two rows of early potatoes. Encourage the eyes to open and grow short shoots, cover up with polythene to warm the soil.
You can get organic slug pellets, based on ferric phosphate , if you dont like the normal chemical metaldehyde.