As a christmas present, i'd like to buy someone a train ticket so they can come up to Blackpool for the weekend.

I want it to be a surprise so obviously don't want to start asking about which weekend they're free etc.

Is it possible to buy an open ticket that allows travel whenever within say a 1 month period?

I've had a look around and seem to be able to find open tickets for the return journey but needs a specified initial journey.

Is there such a thing?!