Hi,
Was a bit wary about installing 3rd party app onto my iPhone.
In the end I went to Apple tech chat & basically deleted the BT account, switched phone off/on & added BT as an account & it seems to have worked. I did ask what they thought has caused the problem but they were very sheepish & couldn't give me a definitive answer.
At least my emails are working now:)
Thanks to all who tried to help.