Surely the whole thrust of the series is an oh-so-gradual but natural process of bringing Nicola and Patrick together?

No, no, no. It maybe looks that way because the series ends with Run Away Home, but that wasn't planned, it's just where it happened to stop. Run Away Home marks a real falling off in the series anyway - can't help suspecting that's why she didn't write any more.

I hold to Jan Scott's comment that lifelong friendships are about as common as unicorns...and by the same token, people are unlikely to end up with the boy-next-door they fancied at fourteen.