Importing Gift Aid records
You can import Gift Aid records with Import Contacts, but as they are as they are multi record fields, you have to use the ... option which is hidden away. You need to click on the ? help for Import Records, which, at the end, gives you a link to the Import Multi-value Custom Data screen. Obviously you have to get your data into a suitable csv file to import and will have to add the contact id to match to the contact record (but easy enough with an export of all contacts and a lookup - checking duplicate names) or use external id if you have used one for the import of contact data.