2663: CTRL+SHIFT+S

The ten unclued lights comprise five pairs, as implied by the title. Elsewhere, ignore one apostrophe.

        Across

   1    Leaves evening party, returning by church (8)

12    Rag Conservative, reluctant after defeat (10)

13    Sad rake unpleasant with no love in sight (6)

15    Nice No. 1’s changed, according to singers? (8)

18    Where the result of perks may be enjoyed (6,3)

19    Calais etc unexpectedly austere (9)

25    Maori dance twice caught cycling shorts (6)

27    Footballers clutching tight back ligaments (6)

29    Ditch possible outcome of amusing quip (2-2)

30    Yvette, now and then one chilly sort? (4)

32    Resorts across Channel sent back nationals (9)

34    Elbow hit with a...