I know (or think I know) how to choose alternates, but as I wrote earlier I wondered if anybody can come up with a reason for choosing Southampton in that scenario. It seems to hang entirely on the unlikely scenario of Bournemouth getting shut down.
It is indeed possible that the examiner in question had AOC criteria in mind, not realising that they are perhaps inapplicable to a private IR.
He was certainly highly specific on that convenience should not feature at all in the choice of alternates or the decision to take one; an admirable and correct and proper attitude I am sure.
Another examiner I flew with today (just some practice) was equally puzzled.
Incidentally I do think that "usefulness" should feature significantly in the choice of alternates. I would not file as an alternate an airport whose locality is an absolute sh**hole (and there are plenty of such) because the incentive to divert there is going to be zero except as an all out emergency with no options left. Private flying is meant to be enjoyed - it is damn expensive enough... If I was going to divert and had various options I would ask passengers where they would like to go (ILS and a decent place to eat would probably feature strongly).
Let's face it, despite all the supposed procedures, even the most famous airlines frequently choose alternates picked for practicality (vis that famous 747 flight from the USA to "London Manchester" with 1 engine shredded on takeoff).
Lydd can be an excellent weather alternate and indeed was the only place open for many miles around the south when I flew back from Tempelhof once. And even it closed minutes after I landed (OVC001 or so). You just cannot realistically get out of there, short of flying out the next day or whatever. For some reason, Lydd often escapes very low cloud which shuts down much of the south east GA access.
In places like Greece one often has no option but to file an alternate which has no avgas, but that is rarely the case up here.