Boris Johnson has given a strong hint he WILL work with Nigel Farage. Proof the Tory Lite Brexit Party is working with the Tories and is full of hordes of Tory defectors. If you vote for Nigel Farage you will get the Tories (or even worse you could even get the LibDems as per Brecon) by default.
So; if you want Brexit but you don’t want to risk getting the Tories, the only sensible way to send a message is to vote UKIP. Vote UKIP get UKIP.