Hi Neil,
you're right about wing root - got the same, although at first I thought it has to be done this way (stupid me). I have noe idea yet how to repair it.
I had no problem with horizontal stab, everything went quite smooth except one strut which I have broken and had to sculpt some replacement.

Anyway I can't blame Airfix for that.
According to my references splitter plate in the chin radiator was removed after E-3 so since we talk about E-4 here it's not a problem for me.