Call the Exec Club number and there's an option for bookings which include hotels, car rental etc. If it doesn't show up then the agent answering will put you through to BA Holidays.

IIRC, BA Holidays can then set the booking up for you, ready to UUA, and take payment authorisation for the base amount.

They will finally put you through to EC again to arrange the upgrade and the additional fuel surcharge collect.

For that reason, it's best not to call any later than 7pm .

If you're attempting to do something which can't be booked online, it's worth asking for the offline fees to be waived. In theory, they are only waived if ba.com should be able to complete your booking but can't - but that rule may not be applied in every case.

More generally, the 'risk' referred to by nh1980 above doesn't apply in a WT+ to CW scenario. The ET to CE upgrade (or indeed WT to WT+) requires the underlying ET/WT booking to be in a flexible fare bucket, hence the high additional cash collect reported.

As all revenue WT+ booking classes are UUA-able, there's no real risk in booking online and upgrading offline - other than the time-delay which may result in upgrade availability disappearing between the PNR being issued online and getting through to BAH on the 'phone.