After a night of Lau Gar (one hour) and some fierce sparring, I did some deadhanging (for climbing strength).
1) 4x30s - 3 minute rest (One armed, four fingers)
The Lau Gar was my warm up! I did it fasted again and got the same feeling of sharpness although the teeth grinding (whilst still evident), was not as bad. I had my usual strong coffee at lunchtime so intend to repeat this experiment without the coffee next week.
The fasted workout definitely suits me and is something that I will continue with - especially where balance and other skill is required.
I ate late, and I ate massive - thus explaining a slightly disturbed sleep.