Ukips rise in support nationwide is scarcely eve relevant. You know as well as I do that power in British parliamentary elections is won through the key marginal seats. Ukip have no established base and very little chance of winning more than maybe a couple of seats at best. As gay state has already said, all they will do is bleed protest votes from the Tories (and don’t kid yourself that most Ukip supporters aren’t disgruntled Tories) in their marginal (and even strongholds) and help Labour get in.
By that logic, no party should ever try, because they don’t have strongholds? These things will come in time.
The only real evidence we have is recent by elections and they have taken votes equally from various parties although it would be true to say historically they were a Tory protest party.
I and many more will not be voting for a conservative party that is not conservative. If Labour gets in so be it.
But the Tories have got that bad. They desperately need replacing even if it takes another few years to fully do the deed. If any party should retreat for the sake of conservative unity, it should be the Cameron abomination doing the retreating.