Wife and I have 22,316 miles, and 540 TPs (all earned from a single trip in F not paid for by us) each, in two separate accounts.

To my pleasant surprise, it seems we can fly LHR-ATL for £554 in WT over the Christmas period, or £630 for WT+. Obviously we can easily get to 25,000 miles, either with cash or Tesco points.

A quick check on ba for 'book + upgrade', shows that there's no problem upgrading the outbound to CW, but the inbound is much more difficult.

No problem, we have just short of 50,000 miles = 4 one-way WT+ -> CW upgrades for wife, me + 2 kids.

Only thing is that I don't want to load up with miles, either by cash or Tesco points, to find out that they don't have the availability for all 4 pax. The availability is showing in the booking engine for 2 + 2, but I have no way of knowing whether the price for 4 will be the same as for 1. Are all WT+ fares eligible for upgrade to CW? I.e. if I check the cost of 4 WT+ tickets at ba.com, that should be the price I pay?

Secondly, I obviously don't want to make the bookings separately and risk only being able to complete one booking.

How can I marshal these?

Finally, I take it we would earn 75 TPs on the upgraded LHR-ATL outbound, and taking us over 600. Would we have lounge access as silvers on the way back (which of course would be in WT+)?