Do I have to read Lawrence Durrell's Alexandria Quartet?

I loved his Stiff Upper Lip and Esprit De Corps- also about British diplomats but funny-but couldn't get through the trilogy.

I read the whole Quartet last year and from your initial reaction I'd say no, don't read it. Three of the four books are very much in the same vein—somewhat stiff relationships, unexplained jumps in perspective, a faintly clumsy/condescending authorial voice—so if you truly 'hate the style' for those reasons you're going to find it hard to get over, unless you love the setting.

For my part I did find the setting fascinating so it was worth persevering, and there were from time to time long, almost stream-of-consciousness passages—an encounter with child prostitutes, or a long ride through the delta and desert with a significant character's brother—which were almost transcendental and the payoff was immense. It doesn't sound like you're in a mood for that.

Interestingly the third volume, Mountolive, isn't like that, but is the straight-down-the-line story of a British diplomat caught up in those wider events. It's the book that enabled me to make overall sense of the thing. I never thought of how it would read on its own but, if you did want to exhaust every possibility before abandoning, you could give that part a go and see if it sticks.

Absolutely this. I tried to read Durrell and did not manage to continue. Fortunes of War had me gripped though, very character driven.

Nope, not at all. If it’s the history aspect you’re interested in, maybe try Olivia Manning’s Fortunes of War.

But be warned, she is rightly criticised for an incident at the beginning of the first book of the Levant trilogy, which she took from real life and ran away with in a very unkind direction.

None whatsoever. Life's too short to force yourself to read something that doesn't click with you.