Thanks Jono
The penny finally dropped and I've got the theme. So far, I've found one near me. Unfortunately, it misled me into thinking the theme was animals. I've had to go back through some answers and identify the theme words. So far I have identified three theme words as the answers.
I've still got lots to do but am making some slow progress. I don't think I'll finish today.
I am puzzled by a few:
51d I have ?I?E T?A I'd assumed the definition was a drink. Are my letters right?
29d I have an answer, but it is not a word I know and I can't see a theme in it. As a result I can't get 36 ac. I have ?N?L???R for 36ac - are my crossers right?
My top left (NW) corner is practically empty. Could I have hints for 18ac and 33ac please. I thought the latter was an anagram, but have failed to solve it.