Remember you can apply for a LH position at BA, succeed at assessment and end up in shorthaul. You join an airline, not a fleet. You then become 'frozen' for 5 years and can't 'bid off' the fleet unless the company requires you to. I have two mates in SH who say it's a shambles. IAG are giving it a constant prod due to its poor profit making abilities (the shorthaul part of the business). You have cases of SH skippers bidding for right seat LH positions as the writing appears to be on the wall. Do some serious research on how IAG dismantled Iberia shorthaul, replacing it with the 'slick' Iberia Express/Vueling Lo Co model. That's the fear within BA SH.
The LH recruitment is for the 744. If you end up on it you'll be very junior, subject to blind line for a lengthy period and will remain junior as the fleet is on the out. Time to command is 20 odd years for LH. The 777 is covered by internal bids and is unlikely require any DEP hire. Maybe its not the be all and end all it once was however for those wanting the UK, it's probably the best you'll get. Wouldn't say it's a 'no brainer' but I have no experience of the situation within CX.