Looks like we're back to square one! A week on scent swopping and peeping at each other through one inch gap in the door, new cat is stalking up to old cat, through the gap I mean, looks like he'll either pounce for her, or leg it scared! He went into the room she was in, and she dove for him (this meeting was unintentional, he'd run out of his room when my daughter opened to door) I've taken him out of his room, put him in the kitchen, and let old cat explore his space/bed etc, she doesn't really look interested.
Yesterday evening, I held him, and took him into see elder cat, she was calm, he was scrambling out of my arms to get to her. But in a bad, angry way.
So, I've been out this morning, bought a "felway friends" plug in, I'd been using some spray called baephan or similar, smells terrible, but the spray action seems to cause them both concern.
Good news is at least old cat starting to settle down a bit over last few days, she went to ground a bit when new boy came home.
Hopefully this time next week, they'll be friends (or at least not trying to kill each other!)