Thanks chaps
Installed Norton on my laptop OK. Unable ditto on iphone & ipad mini. Phoned BT - their response was 'Norton products can't be installed on Apple hardware'. Norton website says 'Norton protection that is provided through BT is currently not available for IOS devices'. Brilliant!
The old cynic in me wonders whether the BT directors have been bribed with an extra bonus to change to Norton. But that would be unethical, wouldn't it?