[duchy]

I never wait but proactively contact the airline .
In your situation I'd be checking out all my options first as I know from experience often the airline's idea of the most suitable and mine differ considerably!
As well as the BA only options and their partner airline AA flying from a regional airport I'd also run all my "other airline" options, like Lufthansa via Frankfurt or Aer Lingus via Dublin as things may have changed with them in the meantime and the flight change would give me the option to cancel and rebook without charge.
One year my friend's teenage son announced he had "forgotten" to book holiday from work and his step father was resigned to losing his fare until a change popped up and we were able to cancel him off with Full refund.