How long does it take for the merchant account to transfer funds into my bank account?

Sage Pay sends the details of your transactions for settlement once every 24 hours.

In some cases, your merchant bank may impose a settlement or funding delay on your merchant account, which means that your funds may be held by your merchant bank for a number of days before releasing them to you.

This is something that is assessed by your merchant bank on a case-by-case basis and must be agreed to by you before your merchant account is approved.