Unfortunately if you eschew OLCI and wait until the desk opens at the airport you will find all the pleasant seats are gone and you are stuck in 63E with your non-reclining seat back against the rear galley.
And I wonder why the US, with its ridiculous over-zealousness for security matters, can nevertheless manage to have standby pax down at the gate whereas in the UK we cannot manage it. Once again it sounds like carriers just not organising themselves for passenger primacy, or airport and airline blaming it on each other. Goodness, in the US even non-travellers, such as those bringing UMs to/from the airport, can, provided they jump through the security bureaucracy, get down to both departure and arrival gates.