A couple of parsing queries - it's a Paul McKenna so no surprises there - he often confounds me!
5 down) Somerset's channel blowing the lid on gullible - one looking up (4)
I have REEN, but can't make sense of "one looking up" in the wordplay.
8 down) Among Scots Mister Johnny Hallyday's the pinnacle of rock (6)
I have NEEDLE, and assume the French reference is to LE, but don't get the "among Scots Mister" bit.