I'm booked on points for June.
Thanks for the advice all
I emailed the hotel and asked for 5 nights rewards booking on June as the website is restricted to a month ahead. I requested the dates and added my titanium number, they replied within 24 h with confirmation of the booking.
The email addeass can be found if you search Google for 'courtyard Tokyo Ginza email', the link is on the first page. I believe the email address is also on this thread, just search for email.
Thanks all