It also depends how much work you are willing to put in to the exams this summer. A levels are largely more important, however if you are able to bring your GCSE grades up and still do well in your A levels, then why not?
If you think that the English GCSEs will affect your getting into university (i.e. a competetive course, or an essay-based course) then I advise you retake. Otherwise, just focus on A levels.