I have completed OLCI and used ITCI so this should not be a problem. Assuming that you have not been able to allocate seats as BAEC Blues I would guess that you would actively want to OLCI to get the best seats left available.

I have never used the J showers in the Wing but I agree with bensyd the Wing is infinitely preferable to the BA/QF Lounge, I am less sure the same can be said for the Pier.

I see no link between the ITCI and the Airport Express except that ITCI must move checked bags using the aiport express, there is no requirement to travel on it yourself.