Jim,
Ukip's racism has been debated and proved over and over again

No it never has. Remind us of this proof.
You linked to an article where some people claimed a poster was racist.
The police decided it was not and took no action.

I do insist I am not an extremist, and await an example of extremism from me.

There is no obvious increase in their popularity, no sign that they have made any grounds as a party,

Admit you are wrong about that Jim.
Their vote has steadily increased.
In the general election Ukip came second in 118 of the 650 parliamentary seats.
They had more support than the Lib Dems and half Labour's vote.
"Overall, Ukip secured 12.6% of the vote, an increase of 9.5 percentage points from the 2010 election, the largest of any major party and more than three times the size of the SNP's improvement."
https://www.theguardian.com/politics/2015/may/09/margate-ukip-greens-electoral-reform-farage