Yeah, this is the problem with the rarity of the "honest politician".
You can do exactly what I've done every year... vote for the person you think would represent your views and make a difference. That's led to me *not* voting at all since I was eligible. I very much doubt I'm the only one doing this, considering the turnout at the average election and particularly the proportion of less-than-middle-aged people who vote. In a choice between two evils, I just don't choose - it's the only sensible option when it is available (although I'm sure the UK are working on Australia-like rules where you MUST vote - I would have to tick box 1 on year 1, box 2 on year 2, box 3 on year 3, etc. in those circumstances, or flip a coin).
I have chosen to use my freedom to vote for whoever I want to, to vote for ***ME***. ***I*** can perfectly represent my views, ***I*** would do exactly what I want a politician to do and only ***I*** can do it in the way I want. Thus, in the absence of a vote for myself (because apparently democracy doesn't allow that in general - I can't vote myself to be prime minister at the next election, I have to tick one of these boxes to select someone I've never met) I will vote for the next nearest candidate which is... erm... nobody. Problem solved. I might not be helping the next great person to power but equally I'm not electing the next Hitler, either. I consider that an all-ways-win for my country, given the current state of politics.
P.S. Laugh at old Boris all you want... he's London Mayor and he's doing a bloody good job considering. I don't even know or care what political party he's supposed to represent (a politician is a politician no matter what colour you paint him), all I know is he's made some very good decisions from my point of view and no major cock-ups.