I'd think the missing tail and haircut would knock down value. Frizz may do on Sweetheart depending how bad she is, as a Seven Character she is probably more sought after.
I've seen dragons regularly sell around £30-£40 but it may depend on condition and so on. (P.S they weren't sold with alternate anything, they were sold with the same princesses as were sold in most places). It also depends on which dragon. In my experience Fiery and Flash are harder to find.
Movie Star Wind Whistler, if her hair is still pink, she'll be worth more.
Nurse Ponies tend to go up in value quite a bit if they have their hats, but it also depends on the condition of the symbol as well and whether it functions.