Presently looking at a flight from Heathrow to IAD / Dulles (Washington DC) with MFU possibilities.

There are 4 flights on the day I want (Thurs 27th Oct) that are open in WT.
3 flights are open for WT+ (one around 14:35)

If I decide to book the outbound in WT+ and use miles to upgrade to CW, the only flights available are BA0217 (10:50am) and BA0293 (17:10), the latter not arriving until after 8pm so probably not getting into the city until 10-11pm at the earliest?

Did really want to try out the lounges (never seen any BA ones at LHR although probably all the same?) and have a good look at T5 but the early flight means I can't really do that and would require staying over in a hotel. The later flight(s) could involve me getting an early train (arriving at LHR before 10am if need be) and getting plenty of time to do my thing.
As already said, the later flight loses me a lot of time in Washington and then Thursdays do tend to be the mostly costly night of the week for hotel stays and I won't really get to enjoy that bit.

No CW availabilty the day before on the outbound by plenty inbound.
Return flight from IAD is on the 7th Nov as I'll be doing a TP run around the 1st-2nd Nov to get silver.

So, considering the route and the flights are generally 777s or whatever (3/4 class), is it actually worth flying CW on the available two flights or just slumming it in either WT or WT+ outbound? (WT+ books into T class so no idea if I could upgrade with miles later on should anything open up)

Added: Did consider flying into NYC but nothing at all there. Then looked at Phildelphia and zero availabilty there as well.