I have had a 3 bookings with changed domestic connections to/from long haul flights both GLA to LHR and LHR to GLA in the last few days, only one of them asked me to accept or choose an alternative flight the other 2 they simply changed my flights and they showed in MMB (A quick call sorted this out to better connections than the ones they were imposing). The existing flights which they cancelled are no longer available to book.