I've known a couple of occasions in the past when students became disenchanted with their distance learning courses and decided to join a residential course. In both cases they had a number of exams still to pass and little time to do it. I wrote to the CAA requesting approval to cancel their previous passes and start all over again. The CAA agreed, but only because the students were changing school and courses. Given the emphasis that the CAA placed on changing schools and courses, I suspect that unless you are also doing this, they will probably reject the request.
Do you really need to get started on your new set of exams immediately? As far as I am aware there is currently little or no demand for newly qualified 200 hour ATPL holders. Rushing to get qualified then sitting around waiting for a flying job doesn't make much sense.
Would it not be better to study hard for three months while your current 18 month exam window to expires, then start retaking some of the exams?