Sorry for your loss. Try and be calm, ime money, wills and family are generally a difficult mix.
Personally I would assume you are going to get nothing from the Cyprus account, I don’t know if a Cyprus bank would even recognise a UK probate (ie your authority to ask for the money). Also as above you have UK and Cyprus law issues, who knows it could be the norm there for all the money to pass to the surviving account holder automatically.
Do you have a relationship with the gf ? If so you could ask for half the money, tbh its possibly gone now your Dad may have told the gf it’s to be hers on his death, it could have been a gift to her etc …
Good news he didn’t transfer more over really
Best of luck