Well this was certainly a step up in difficulty from last week's puzzle, or any others this year, for that matter.
Grid B was straightforward enough but Grid A was a different kettle of fish, which took me a long time to get to grips with and it was even longer before I had enough of the longer answers to be able to start filling it with any confidence. Eventually the hidden instructions became guessable, and this helped especially with the skipped-letter clues.
The finale was something to behold, although not difficult in itself. The mechanics of the grid must have taken an age to devise.
To anyone wondering whether to give up, I'd advise pressing on for a while. You'll probably be glad you did.