Robin Robin is a 30-minute film, made by Aardman Animations for Netflix. So, unlike regular movies (where Netflix might only buy in the streaming rights for a year or two), Netflix hold the rights in perpetuity. So, while Netflix
might licence another broadcaster to show the programme on Freeview at a later date, there can be no guarantee of it.
Netflix doesn't offer free trials (
https://help.netflix.com/en/node/16282 ) but you could sign up to the basic service for a month for £5.99 and then cancel. (There's no ongoing contract involved).