Agree the clue numbering could be misleading. Separating down from across was helpful but it may have been better to leave them unnumbered and listed only in order of their answers size.
I suspect this crossword started very differently. Several of the unclued entries can be defined by the sum of two primes. It is possible that clues have been removed and clue order randomised to make it more difficult.
In my view it was a tad easy for a Listener and listing all clues - both across and down - in order of size of answer without numbers might have been an option.