Hello Colan and welcome to CC.
I lived in Stockholm for 14 years before moving to Oslo four years ago (but I'm from Essex originally).
Post your stats on here and someone will be able to point you in the right direction for a sizing.
Or even better, go to a Nishiki dealer and get them to fit you out in the shop.
Nishiki are good looking bikes - I nearly bought one just before I left Stockholm.