"After a few texts back and forward he asked me to meet him for drink when one day when I returned from France - I was there with work - and he sent me a 'xx'.
A week passed and he didnt message! So I messaged him to follow on some chat we had....."
He suggested a drink but didn't follow through (within a week anyway)
He immediately sent me a voicenote, said I was great to hear from me and tnat he had a couple of long shifts coming up but he would call me. He texted over the next l couple of days later to ask how I was doing and tnat he was on his shift but would be off this week and he would call me to meet.
5 days have passed and no message from him again!*
He suggested a meeting but hasn't followed though in nearly a week.
You prompted him the last time, I wouldn't prompt him a second time.
He may be busy etc. but it takes a few seconds to send a message or make a quick call.
If he's interested, he'll contact you.
You're not making yourself look busy, with plenty of options, desirable etc. by prompting him, again.
Anyway, you don't know for absolute certain that he's single, do you?
Single or not, he may have expressed disappointment at you not contacting him in Toronto because he thought if you two met up there it would easily become an enjoyable, fun, serendipitous fling.
If he was all that keen or available to date you in London, you'd think you probably wouldn't have had to prompt him to contact you (after you returned from France) and prompt him now, again.
Maybe he's not single and can't fit you in easily so that's why he's not contacting you quickly with plans.
I would just leave it. The ball is very much in his court.
It's only been 5 days (though he hasn't contacted you when he said he would (this week)?), I'd just leave it with him.