I booked a flight BHX-CDG-JNB for late December, with the first leg on BE metal, as an AF codeshare (all one ticket).

I have received an email stating that the BHX-CDG leg is cancelled and I have been rebooked on AF metal 3 hours earlier than expected.

This is really not a huge big deal to me at all, however my plans have changed slightly and I would now like to return to ZRH or MUC instead of BHX, possibly a few days later.

Is the 3 hour earlier departure a good enough excuse to cancel and get a refund, then book something else?