After three days of trying to get my BT mail back on outlook I have finally resolved the issue. When we transferred from BT to EE broadband (same company just different name on bill) BT downgraded our emails to "basic" without informing us. There is no way of testing or knowing this, only by phoning BT. Apparently Basic emails cannot be used on outlook! I have now phoned them and our email should once again be standard and function on outlook.
So if you have swapped to EE and your emails stop working on outlook just ring up BT and they will swap them back. Easy once you know!