Well, wise women of Mumsnet - thanks for you advice earlier (apart from you, Ladymud - for your insinuation that I was on the verge of becoming an OW.
38 years and still haven't managed that (despite plenty of opportunities) because my moral compass is dandy. My cocklodger radar, not so much so, but I ain't going to be anyone's OW.
Anyway, update:
So I ignored most advice, and we did indeed meet for coffee. And I'm glad we did. I understand why a lot of people advised against it - but I just wanted to see him, draw a line under this and then move on.
I like to think (despite fuck ups in the past) that I am a pretty good judge of character - and I just didn't get what was going on...
So, we met for coffee - and had a good chat.
He was very up front, and open - I told him that it was cards on the table time - and he respected that. Turns out, he IS (as he had said) single and not in a relationship - but boringly, is still in love with his Ex.
Apparently, the relationship was going nowhere, but having met me - and really liked me - he couldn't work out why he wasn't ready to actually start dating properly. He took a bit of time to think about it, and figured out, that it's because he still loves her.
He is very sad about it - but said it wouldn't be respectful of me (or him) to keep seeing me, whilst he still felt this way.
Could of course all be BS, but I don't think so. So we had a nice chat, I wished him luck, and we said goodbye.
Now I am clearly quite gutted, as I really, really quite liked him. But at least now I know. And can now move on.
It sucks, it's bad timing and I'm feeling sad etc etc. But at least this is a man who I don't have to write off as a cocklodger - he's been honest (albeit he took a few days to get there) but it gives me some hope.
Yes, of course, he should have sorted his shit out before going on a date with me. But sometimes you just don't know if you're really over someone until you do meet someone else. And, as someone pointed out upthread, we met through work - he wasn't OD, it wasn't as if he was actively looking, whilst still not being over his ex.
So - conclusion - despite the many shit relationships I have had, maybe sometimes it is better to pursue the truth - and not just write off weird behaviour as (the bloke) being a wanker. Maybe some of them really are just struggling with a lot of the same shit that we are.
I possibly wouldn't be feeling as generous if I hadn't just drunk about 5 G and Ts, but hey. At least I know where I stand now. And that is wasn't me - it was him.
Thanks again for all the advice Xx