Seems to have played out pretty much exactly as Andy and Matty suggested above.
Emailed
info@werder.de in English, chucked in a rough German translation from Google as well just in case chancers looking for group tickets were ten a penny and they had no time for random foreign language requests. They've got back within two days to offer ten tickets with slight restricted views, €30 each.
Trains between Hamburg and Bremen are pretty frequent and take an hour, and that looks about a 30 quid return.