I extracted the bundle added it into pwnage tool 3.1.5 I updated cydia using pwnage tool (which may be the cause of my problem?)
and then I built a custom firmware and tried to upgrade to 4.0 GM using that firmware but the iPhone kept failing on restore. So went into DFU 1600 error then back to normal restore - error error on and on eventually just restored to 4.0 and decided to wait for another jailbreak.
However if I am doing something obviously wrong here please let me know as I'd rather not wait! Thanks.