The Guy With The Girlfriend

I feel the need to update on the Rains/Pours posts.

The Guy With The Girlfriend is leaving me in a bit of a pickle. He called me on Hallowe'en because we were both out in London. I don't entirely remember what he said, but he'd left the partying early, and I think he'd had an argument with The Girlfriend. He said he was looking forward to seeing me when he visits Leam' this week... I tried to be good and tried saying it wasn't a good idea;
"What about your girlfriend?" - "I just want to say goodbye, nothing more than that"
"Well I'm not going out of my way to see you" - "I'll take you for dinner"
"But your girlfriend...?" - "I'm allowed to ear dinner with friends!"

And despite Genever hopping about next to me pulling unimpressed faces... I agreed to meet him and started looking forward to it. He convinced me (and I convinced myself) that it really is just platonic. You know... two friends, meeting for dinner before one of us leaves the country...
It could all be very well and true, apart from the tiny fact(s) that:
a) we've slept together;
b) he had a girlfriend (that I didn't know about at the time);
c) he's still with that very same girlfriend;
d) despite said girlfriend, we've still kissed when drunk and he repeatedly tries to persuade me to sleep with him.

I slipped it into conversation with Becca this weekend and she went mad at me because she knows what he's like. Then a mutual friend Facebook'd me asking if we're going to be "sleeping/spending time with each other".

But... but... we just had this conversation via txt:
My weekend went from bad to worse. I'll tell you more when I see you. You're still up for dinner, right? - I'm not entirely convinced it's a particularly good idea, but yes. - Why would it not be a good idea??

...and I've not replied. Am I, and everyone else, jumping to conclusions? Maybe he really is over his cheating ways and really does want to see me as just a friend. Maybe I'm just being big-headed and far too assuming.