Importing Contacts where Account Name is non-unique

Importing Contacts where Account Name is non-unique

I'm trying to import Account and Contact data. We have many Accounts where it's the same company name but different sites (eg "Acme Ltd" with branches in Birmingham, London and Leeds).

We need to import Contacts, and have them associated with the correct branch Account - but the Contact Import facility only seems to allow associating them by Account Name.

How can we do this?

We do have additional unique index key data for each Account in our import data, and the Contacts import data references this unique index key data for the relevant account ... but I couldn't see how to use this to achieve what we need.