I live in the London area, have a Revolut account and am aware of Monzo but have never heard of N26. I agree with the above poster that their advertising cannot have been very good.
Worth noting Revolut do not have a UK banking licence, and your funds with them are not protected by the Financial Services Compensation Scheme (FSCS).
They have an EU bank licence and funds are thus protected under the EU-wide protection scheme.
When they came out in 2018 I remember they advertised heavily for a few months. But since then I have not seen any advertising in the last year or so.