"hey, had a really lovely time the other night, if you're free, perhaps we could catch up again soon? If you're not free yet, that's no problem just let me know your thoughts. Take care, xxx"
I like the first part about the lovely time..I'm not sure about the rest though. Part of it feels kinda needy. I would prefer to be a little more flirty or funny - he's a really funny guy. I want to keep things light - while letting him know I'm interested.