Ok, Solved it, thought i'd post my solution.

In my tpl_header.php files under tmeplates, all my links were relative i.e
'<a href="/index.html">'

I had to change these to direct links in order that they didn't change to https when clicking on th login button.

changed to

'<a href="http://www.mydomain.co.uk/index.html">'

Problem solved.