Hi Jono,
Just a general point to mention that, like you, I solved the numbered clues first - the fact that a few are anagrams helped enormously.
This then allowed to place, with some degree of confidence, one of the long 13 letters clues - another anagram.
But.... all that I've done is in the central are of the grid so I take note of the trickiness you speak of in the corners:-)
Anyway, I need a rest so have put it aside for a while.