"I'm just being friendly, but I must be coming across in a flirty way"
I have to say you do seem to be missing big, obvious flags that this guy's intentions are more than just being friends. By continuing to talk to him after he's made his intentions pretty clear, he probably thinks you're up for it, when in fact you're just being a lovely nice person, while missing the bloody obvious!
He said:
"It's definitely no hardship saying hello to you..... I think that you are lovely." This for a start isn't something you say to someone who is just a friend! He's chatting you up. This is the point at which I would run a mile from someone who has a GF, and remind them they're not single!
Your reply, whether you realise it or not, reads as if you are acknowledging his flirtations ...
"Thanks, I wasn't expecting a reply anyway (I guessed you probably don't get on facebook much) and to be honest was really worried I'd have overstepped the mark contacting you. So thanks for such a lovely reply."
... thanking him for a lovely reply for example when he's so obviously talking to you as someone he fancies has possibly given him the green light to flirt with you, as far as he's concerned.
He later says " "No worries girl. It is difficult for both of us. I liked you the first time I saw you and our brief chats did nothing to put me off lol."
This is also him flirting with you / testing the waters, as is asking you what your "situation" is (i.e. how available you are).
You say: "I tend to take things at face value - if he'd wanted a shag I expected him to just say it." But he's already said it - reading between the lines of his messages he's shouting it at you! From his position he probably thinks you understand his intentions.
You do come across as a lovely person, but please forgive me for saying, really quite naive.
Incidentally, there is nothing wrong with making friends with the opposite sex! FWIW I have lots of male friends. However none of them tell me I'm "lovely" or mention my appearance ever, or feel the need to remind me they have girlfriends. They treat me as one of the lads.
If you find yourself on the receiving end of flattering comments about yourself, and your looks, and men telling you they "like you" - newsflash! - they're trying to get into your knickers! If they're single and the feeling is reciprocated, great. :) If they're attached, it's not good news.
"This guy is still texting...dont suppose that means he's any more genuine? Just checking ;)"
Nope, just a genuine slimebag I'm afraid 