I don't think the fact he's using an expensive dating service is an indicator of looking for a serious relationship, I'm afraid.
He clearly has plenty of money if he can afford to drop £300 on a date - why weren't you paying your share, anyway?
If he's got that kind of money, why trawl Match, POF, Tinder?
Outsource it, get an agency to find the women for you. They'll probably (because it's paid for) be reasonably educated and have some money too - if that's something he wants to filter people on.
This way, he gets regular dates with intelligent women, found by someone else - which might lead to something. Because he might be looking for serious - but that doesn't mean he isn't happy to have casual along the way.
I always think there's something a bit odd about a man paying for a date - so that would have put me off for a start!
Just take the positive - you had a fun night, you enjoyed the sex, you had a reminder that it can be bloody hard work!
Don't text - if he wants to, he will. I'm usually all for just texting, but it's been long enough.