It seems to me that the 3 thematic items to be found at the end work much better if they are 8, 8 and 5 rather than 8, 8 and 7. Curious to see if others agree.
Thanks, tatters - I'm struggling to justify one of the thematic items in Chambers (although I'm sure it's right) and it isn't the one in Collins.
I liked KevGar's clues - and the gimmick was fun (I think).