Liz didn't want to marry Ally because Ally was working class

Who still sleeps in a bunkbed and has superhero posters on his wall. Yet we're invited by the ending to think that all's ended relatively well and class is never mentioned.

He was batting outside of his league because he thought being a Scottish soldier should make him irresistable and she was the middle class false modesty madam who thinks that she can slum it for a bit (so condescending to anyone older than her, did you notice?).

In real life, we could be looking at Ally killing himself over this - no wonder he chose to be a soldier again - his suicide in the line of fire could then be looked upon as heroism if he dies.