Hops changing sex?!

I used to live in Italy where hops grows everywhere like a weed.  Before moving back to the UK i wanted to bring a plant home so made a note of where a nice female plant was growing and then dug up the rhizomes in the winter.  After 2 years growing in the UK, last year it had no flowers and this year it only has male flowers!  Im 99% certain I got the female rhizomes but confused as to why it is now only producing male flowers.  Is this possible and will it change back once it is a bit more happy and established and gotten over our colder summers?