1. I do not seem to be able to add any new controls to the basic Task &
Details form as the controls button is greyed out. I am only able to
add to (P.2) (P.3) etc

I would like to add three new fields to the first screen.

1) Not possible; known issue. See http://www.outlookcode.com/d/taskform.htm

2. The field for contacts, at present this does not allow me to amend
it.

Amend it how? In any case, since the Contacts controls are tightly bound to the Links collection, you won't be able to change their functionality.

Also, it looks at the Contacts folder in MS Outlook for data. I
would like this to validate against our exchange GAL

Not possible. The Links collection is specifically designed to link to Outlook contact. It does not function like the Recipients property of a MailItem.

Lastly, is anybody aware of any articles / books on reporting on tasks
in Outlook. eg Overdue tasks, tasks in one category etc.. (basic mis)

See http://www.outlookcode.com/d/customprint.htm
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx