Now, with a prepaid card there's no 'loan' involved (except from you to the bank), so does it provide the same level of protection?
No, needs to be a 'credit' card, i.e covered by consumer credit legislation. Debit cards don't provide additional protection either if the supplier doesn't supply. And even if a credit card, the amount needs to be above £100 before the bank is jointly liable for the supply, so the real cheapo deals will not be covered anyway. No chance of Ryanair going bust in the near (or even distant) future though so I wouldn't worry about it.