IPhone Whatsapp number transfer?

Backed up everything to iCloud.
Getting new phone, however, whatsapp was attached to my US number and i'm putting in a UK sim. Would it automatically keep my USA number?

I'm going to change my number and/or phone, what should I do?
http://www.whatsapp.com/...l/28030001

Everything you need to know about changing your number for Whatsapp, should be right in that link above.

Whilst in the whatsapp app go to settings then account and then press change my number so you can transfer your stuff on whatsapp to your new number