Hi
@MartynRich, I use the iRig mic Studio. It is nice and small, therefore very portable. Extremely clear sound, though maybe lacking a bit of warmth. To compensate for that I use it with an app called MicSwap Pro, which is meant to simulate classic pro Mics used in the recording industry through the years. Obviously, it can't really do that for a few quid! But it does add some nice depth and texture all the same.
Good luck with your quest!