It probably isnt worth the money but it would still be awesome if it happened. I'd love to see high speed rail or maglev running down the east coast of Ireland down from Dublin, through a rail/road tunnel and then following the Great Western railway / m4 corridor route though Wales' major cities, then to Bristol and all major stops into London! That would be absolutely awesome, however a tunnel along that route would be longer than the Channel Tunnel and I doubt is likely happen in our lifetimes.
The best bet is probably to invest more in air and sea transport.