LMP UK,
Check your MYWAY selection. If you picked Option 1, upgrade, you will receive 2 breakfast coupons. Typically it will be just be for continental, but as Diamond, I have been allowed to have full at some properties. It really varies. Can't remember what the Caledonian did.
Given you have already been upgraded, it sounds like you picked Option 1. BTW, the Caledonian Hilton is v nice and as Diamond, I received a bottle of wine and chocolates delivered to the room one day, the next a plate of fruit and a little bottle of whiskey.

If you do NOT have Option 1 picked, you are not entitled to the free breakfast.