Potential problems should be eliminated one by one. Based on the "grey veil" description by OP, it isn't entirely clear to me whether he's just experiencing low contrast, or an actual fogging. I'm assuming (perhaps incorrectly) there is fogging, in which case over/underdeveloping is not going to improve things.
Rule out fogging (from safelight or enlarger) first with a proper safelight test etc. If non-image light is completely ruled out, then look for other problems which could lead to low contrast and/or veiling. Check that processing is as per Ilford instructions (including fixation - incomplete fixing, overused fixer). Then look for problems with the enlarger. In addition to potential filtration issues, it could even be something like a dirty lens.