So sorry to read this OP.
I will briefly repeat what I very often do on these threads and it was only after it happened to me that I realised there was a script that all cheating twunts seemed to follow. I wish I'd have been aware of it when I first discovered the cheating.
Anyway, deny, delete, minimise...
Deny it happened, delete texts and emails, then when you present your evidence (screen shots, bank statements etc) minimise...
We only messaged, only met once, only kissed and my absolute favourite, we met but I couldn't do it, yeah, really......
My OH stayed in a hotel (well premier inn, classy) all night with Ow and I understand how that makes you feel....
What you need to be prepared for is that they may have met more than once, lunches, days off together, early starts as well as late nights and off sites......
And sadly you need to be prepared that there may be others.....
I can also understand that in your mind you knew there were some issues to be straightened out and you thought you were both working together to resolve them. For me it was similar, I'd instigated the 'talk' given him an opportunity to discuss, and he assured me all was well.
He will need to leave so that you can process this information and decide what you wish to do going forward. He will need to answer all of your questions and have totally transparency with phone and email, all of them, work and personal. My OH used his blackberry for all of his messaging etc. knowing I would never look at it as I thought it was just work stuff....
If you want to get past this and move on with your relationship with him then I would also insist that he looks for another job. And I would take no ifs or buts around that.
Sorry if I've gone on a bit
PM if you'd like to.
We are here for you and we know how you feel...