Geeker, thanks again and now the penny has finally dropped! I actually had the answer for 1d at one point but dismissed it because I hadn't spotted the reverse spelling. 2d still looks dubious to me.
Loved 12ac, though, the final solution filled in on my grid – thought that was really witty!
Don't often post here but I often look for hints. Thanks to all fellow cruciverbalists for help and encouragement.