Simon
All 4 of those are in the thematic 13.
35d- Incorrectly entered letter is E- should start with W instead. Def Long ago all that
5d " " E- should end with G instead. Def waterway in the centre
23a "" O- penultimate letter should be r. Definition nuking device
20a "" G. 2nd letter should be N. Definition Troops' troupe
If you need a nudge let me know