Q: partition delete failed in bootcamp assistant

When trying to remove my installation of Windows 7 the bootcamp assistant failed mid-way through removing the bootcamp partition.

The issue here is that I can recover the space but I can't make a single Mac HD partition anymore.

Disk utility says - "couldn't modify partition map because file system verification failed" (see pic)

I've been through the discussions and can't seem to find an answer. Trying gdisk and other command line routes to try to get my partition to unite again, its a 2TB drive and the Bootcamp partition was 300GB so I'd really like to get it back in one piece.

How can I make it one Mac HD partition again??

Been here for a few hours and am at my wits end!