Scratching *NEED DEFINITE ANSWERS* Does piggie have mites or not?

There isn't really a way for us to say for sure if he/she has mites, so you might just have to take him/her to a vet. I don't see any problem in treating anyways, though. How often is s/he scratching? A few times a day is normal.

The only "FOR SURE" way to know, is the diagnosis of a veterinarian.

Unless you want to wait for it to be shipped from the UK, I wouldn't buy that. It's not a particularly good product for mites as it isn't considered strong enough to kill them. You also need more than one box, so it's not the cheap product it looks like it is. I'd order this instead: (broken link removed). It's easy to use, and will do the trick.

There's no way to know for sure that he has mites. They burrow under the skin and are invisible -- the only symptom is scratching, or hair loss if the scratching has been going on long enough. But it won't hurt to treat him with the ivermectin even if the problem isn't mites.