I received the following reply from BA. What they say is incorrect isn’t it? I should be able to get a full refund.

“Apologies for the delay in responding to you. Your flights to and from Las Vegas are still scheduled to operate in August but the aircraft operating your flights will no longer have a First cabin, so you will be downgraded to Club World. If you want to have a refund of your ticket, it will be as per the fare rules, as the flights are still operating. Please let us know how you would like to proceed.”