I found a way to sort of mount the drive and consequently do a data recovery.
What i did was highlight the 'iphone-dump.img' and opened it with 'Disk Utility'. Inside of 'Disk Utility', I double-clicked the 'iphone-dump.img' icon and low and behold, it split into two drives, despite it giving me an 'Unable to attach 'iphone-dump.img' (no mountable file systems)' message at the same time.
I wasn't able to do much with it in 'Disk Utility' from there on, so I opened 'Data Rescue III' and it became available to scan as a 'Virtual Interface' called 'Apple read:write'. I performed a scan and was able to locate my missing photos. It took a while because there were several duplicates of older photos. I think this is because each time I've restored the phone from a backup, data has been placed in a different location on the hard drive. Therefore, it has not overwritten these very same photos that have been on most of my backups for some time.
I wasn't able to find my missing voice memos from the 'QuickVoice' application though. They appear not to be there. I found the existing ones from the recovery. They must be somewhere surely? Maybe the photos are stored in a different way since the photo application is a default app and 'QuickVoice' is a bought app. ?
Ideas anyone