Book a cheap unknown airline and then upgrade?

[highlighters1]

Is it better to say A) Book BA flights for £1000 direct
or B) Book Air China for £380 and try and upgrade, indirect

Option A every time.

Having flown Air China, and on various other Chinese airlines, A.

@highlighters1, If you have other options to BA, they're also worth considering. Depending on when you're going, there are often deals available to specialist agents that aren't on online sites, that typically get published fares only. For example, Virgin, Etihad and Emirates are on sale now and BA will be on sale after Christmas too.
Number of stopovers also affects pricing.

I'd also look at the Middle Eastern Airlines. Qatar are good value and their service is better than BA.

With that price difference definitely the cheaper option.

But it depends on the length of the stop over and total journey.

I'm not a fan of BA but remember getting flight for 5 of us in the January sales to Dubai for £1100. So maybe wait till then.

Or look at other airlines. Have you checked on sky scanner?