Can I upgrade a part cash part miles ticket from BA?

Answer 1

Look at the fare class on your ticket and check the BA site for their upgrade eligibility rules. The fare class will be a letter like M or Y and you can find it on the ticket itself, or on the reservation or e-ticket; it's not the same as coach class, economy class, etc, but rather a category within that level of service. Generally speaking, you cannot upgrade a miles ticket but it all depends on the class your ticket was issued in.

Answer 2

Yes.