This year my potatoes produced what looked like small green tomatoes, what are they and can they be eaten?
The small green fruits on your potatoes are not tomatoes but they are related.
The green fruits contain the true seeds of the potato and if sown in the spring they would produce new potato seedlings.
Whether they would be of any value to you is very unlikely, unless you want to try sowing the seed in the hope of producing a new variety.
The seed are poisonous, so don't eat them.
I have found thin, wiry creatures in some of my potatoes, are these wireworms, and if so, what would you suggest to get rid of them in future?
Yes, the creatures you found would be wireworms, the larval stage of the click beetle.
Wireworms feed for four or five years before they are fully fed and ready to change into the adult form, so they could do considerable damage in your vegetable garden.
Regular cultivation is probably the best control, this exposes the larvae to the local bird population.
Alternatively, dust the soil with an insecticide powder, raking it into the surface of the soil before planting or sowing new crops.
What are salad potatoes, and are they different from ordinary potatoes?
There are several varieties of salad potatoes and they are grown in the same way as ordinary potatoes.
They are noted for their waxy texture and excellent flavour, are generally cooked in the usual way.
They can be eaten hot, or allowed to go cold and used in salads.
What do I look for when buying seed potatoes?
Only buy certified seed, from the National Association of Seed Potato Merchants.
If possible buy loose by weight, and try to select your own.
Look for tubers with at least two small green sprouts.
Avoid badly damaged or diseased tubers, and those with excessively long sprouts.
If pre-packed, choose plastic net bags, avoid potatoes in plastic bags.
When you get them home:
Avoid handling the potatoes too much
Place the potatoes in a shallow tray in the light to encourage sturdy sprouts (chitting)