Complex sentence: With the coming upgrade to the Great Western Main Line, the main line from London to Bristol is due to be electrified, however the electrification will not extend beyond Bristol to, meaning that Nailsea & Backwell will continue to be served by diesel trains.
Split into simpler sentences: With the coming upgrade to the Great Western Main Line, the main line from London to Bristol is due to be electrified. However, the electrification will not extend beyond Bristol to, so Nailsea & Backwell will continue to be served by diesel trains.