The following is from the GUF2 Conditions of Use:
Household Accounts: Any Household Account Member who earns Gold Upgrade vouchers must redeem them personally. Gold Upgrade vouchers are not part of the Household Account pool and cannot be redeemed by another Member of the Household Account. Household Account Members who earn Gold Upgrade vouchers are subject to applicable Household Account redemption rules, whereby the Gold Upgrade vouchers can only be used for members within the Household Account. These upgrades cannot be allocated to Executive Club Members under age 18. An upgrade earned by a member under 18 is allocated to the Head of that Member's Household Account.
http://www.britishairways.com/en-gb/...ditions-of-use
If you can book through a TA and apply the GUF2 at the time of booking, it is a very good way of doing it and you only require I/A inventory to upgrade from CW to F.
To apply it to an existing booking, you would need award inventory in F so obviously more difficult to use.
The best value is I think CW to F through a TA, and although you could compare the CW and F fares and claim £x,xxx's of value it is really whatever value you place on F over CW.