Please continue Brendan, you always give the perfect combination of illumination and encouragement.
Struggled with quite a lot of this, partly due to post-summer holiday exhaustion (well, that's my excuse), so very grateful for all the hints here. 8D a useful addition to my vocabulary (as long as I can remember it!), 28A was previously known but well buried. 18A definitely COD although plenty of other good ones.
I thought 7D and 13D was a deliberate pair, clued in completely different ways, that brought a smile; I think the objection to 1A is unnecessarily pedantic with a loose meaning of 'spiralling'. Altogether thanks to Philistine for a good bit of entertainment and some instruction.
Best wishes to all and thanks again for the hints and company