@Paul ********
Allthough it is correct thet every first time of a stay means you have to report in person, my advice is just to try report online.
It is free, it delivers you a nice filled in TM47 form even when rejected to take with you to Immigration, and some reports in this group showed acceptation of even first time ever reports.
In my own case I have seen rejected and approved online reports, but when you do, just pay attention you need 2 emails, the second one with confirmation and the notification you should keep in your passport.
You are also eligible for online reporting when you don't like to report on day 90 but report on day 80 or so because that fits better in your agenda.
Then the second report is 90 days after the first report, so day 170, and when you stay full 180 days, you have to report a second time, and because that is online it is easy.