I've been in this situation and the answer is NO!
Basically the WTS writes if you spent the night with someone in the same house, unchaperoned, that your spouse is free to remarry. read into this what you will, you dont have to have sex, you dont have to admit to sex, your spouse (or ex) just has to know this has happened.
I 'arranged' a holiday with friends where I shared a room with my partner, I made sure my ex knew about this, NO sex was ever discussed and I would not discuss it with him, but he now considers himself free. I think this is the kind way to behave all around.
I will check out references for you.
Poppy