Missing plus sign before phone numbers

Hi

I imported all my Lotus Notes contacts to Mac address book and icloud contacts from a csv file. I seem to be missing the + (plus) sign before the imported tel numbers which is causing dialling problems. So a UK number which should be +44xxxxxxxxx is just showing as 44xxxxxxxxx

There are approx three hundred numbers that need editing - how can I do this quickly as I no longer have the old csv file.

I guess I need to export the address book to an excel file or csv, make the changes and re-import.

Any suggestions please.

thanks

Charles