You can withdraw consent later, but I don't see how that would affect data processed before the withdrawal (except that storage is processing and the data would have to be deleted). I don't imagine a reputable employer would have any other use for the data, so the withdrawal of your consent might not bother them much. If your application were successful and you took the job, I expect that would establish contract, rather than consent, as a legal basis for them to process your data.

In general, I'm not sure a company processing my data on the basis of consent would stop all processing of my data just because I withdraw my consent. Some processing of some of my data might have a different legal basis. Judging by some websites' privacy options, there's a distinction between consent (opt-in), legitimate interest (opt-out) and other legal bases (maybe neither). I'm confused about website forms that have separate reject and object options for each category of data processing and a reject-all button that closes the form. Does clicking "reject all" mean I have or haven't objected?