Revolut has the same Electronic Money license in the UK as TransferWise, meaning that the money is parked at a regular bank in the UK, but not under your own name. However, Revolut received a banking license in Lithuania in December 2018, and should soon start operating as a normal bank with the standard 100,000€ insurance, demanded by the EU. Yet, if Revolut failed at some point in the future, it's unclear how the Bank of Lithuania would be able to cope with the liability, since Revolut already has more users than there are people in Lithuania[1].

[1] https://www.theguardian.com/money/2018/dec/22/lithuania-icel...