@Jeans,
For 20a Records vowels missing from codes (1,2) I have EPS (due to the "record" in clue - vinyl disc).
This matches with my answer for 1d Chronometer mentioned in news magazine article = TIMELINES and also 15a Added marks for clarity (10) = LENGTHENED.
Can someone please correct me. I'm now thinking CDS may be right, and TIMELINES maybe should be TIMEPIECE. As for 15a, I don't think that's right either. Boy, this month has really stumped me