This is now resolved. I have performed a manual backup and it’s now sorted.
Update
I don’t think it’s a problem with any plug ins that are causing a conflict. I have followed the instructions here (http://codex.wordpress.org/FAQ_Troubleshooting#How_to_deactivate_all_plugins_when_not_able_to_access_the_administrative_menus.3F) and still have the problem.
Thanks
Simon
