"We were on a break"

[LeaveTheClocksAlone]

Opinions please. Did Ross cheat on Rachel?

YES: They were just taking time to think things over and were still exclusive

NO: She had dumped him and he was a free man

No grey areas. Either yes... or no...

"It doesn't matter what Mark was after though, Rachel had no interest in him"

Rachel specifically said if she did it (ie sex) it would only be to get back at Ross.

So she did fancy him!

Did she not come back the next morning and say something along the lines 'can I be your girlfriend again'

That sounds like they were broken up.

I think that was more Monica and Chandler who did that

Again, I don't think she did. I think it was Joey who made those cracks.

Sounds to me like she couldn't care less about him, if she wouldn't sleep with him for the pleasure of it.