Agree with kayty 7.30 isnt early. In show season it concider it a late start if I leave the yard after 5am. I often am leaving the yards at 2am!
I would not plait a horse up the night before unless I knew it very very well. I've done it before and come in the morning to find the horse had rubbed all its plaits off. I had to pick the plaits up from the floor and the horse looked like it had been badly hogged
Anyway no stress plaiting witht thread.
1) Plait down as per normal and secure with a band. The trick here is to get it very very tight at the top (if you can stand on a box to get abvoe the horses neck this makes it far easier).
2) thread needle, double it over and put a large knot in the end. Push the needle through your plait horizontally just above the band (so the needle is going from side to side not back to front) and pull gently untill your knot reaches the band.
3) fold the end on the plait over and wrap the thread around it 2 to 3 times. Then push needle back through the plait to secure it.
4) roll the plait up into a ball then push the needle through from the bottom of the ball to the top of the ball (this is where it becomes important that your plaits are tight). Take the thread round the outside of the plait on the right and push needle from the bottom of the ball to the top, taken thread round the left and push needle from bottom to top of ball.
5) cut needle off thread and tie a knot in it that should be tight enough not to be seen in the plait. Cut off any excess thread.
With practice it should get to the point where you can do similar to this in 20 mins and then you can start experimenting with hiding the thread (i.e not going round the outside) and with paliting to suit a horses Conformation (ie cobra plaits and raised plaits)