Originally Posted by
corporate-wage-slave
Traditionally when BA substitutes an aircraft without a First, they treat it as a cancellation rather than as a downgrade. I doubt you will get the 75% unless you are prepared to escalate it beyond BA and even then it's not a done deal, there have been big arguments in previous years' threads about this point.
On the other hand, because it is part of the Tour Package Regulations, you may get a sympathetic hearing in terms of not getting what you paid for. I would start with BA Holidays on the telephone first to see what they can do to remedy this.
I somehow think that a court would not allow the airline to get away with it, given that the wording in the legislation states
If an operating air carrier places a passenger in a class lower than that for which the ticket was purchased, it shall within seven days, by the means provided for in Article 7(3) reimburse
If the person has a 1st class ticket and BA cancels the flight and rebooks, it will still be placing the passenger in a class lower than for which the ticket was purchased