Wow! That took a while and certainly got my brain back in gear today. Even with "the 17" things didn't fully fall into place with some of the across clues until my usual second attempt "penny drop" moments.
COD? Difficult to pick one this week but I'll go for 4 down just because of the time I took staring at it and the groan that it elicited when things dropped into place.
Doesn't look like there's anyone around at the moment so I can't offer assistance except to say that getting all the "downs" first will make life much easier. So thanks Picaroon for the challenge :-)