My advice is DON’T PANIC! There is no point in phoning BA - right now, agents are flat out & unless / until you are actually downgraded there isn’t anything a contact centre agent can do.

DO come up with a plan B, acceptable to you in terms of a reroute.

I’d also reiterate in the strongest possible terms though that things can change between now and OLCI.

Also, as this is a Holidays booking, this is good as they are known for being uniquely helpful & empowered when things do go wrong.