Hi there ajhp,
Sorry that you are facing some issues with your WD drive.
You really need to provide some more information on the issue. Is the drive powering up? Is the drive recognized by Disk Management and how?
You can start with some basic troubleshooting as just attaching the HDD to a different system with a different cable. In case the HDD is not even powering up, then I guess that either the enclosure or the HDD itself has failed. In that case, your safest bet of recovering the data would be to contact a data recovery company.
In case the HDD powers up, you can go to Disk Management and see how is the drive recognized over there. See whether it has healthy partitions/file system. Depending on that, you will have to use some data/partition recovery tool.
You can try testing the drive with WD's Data Lifeguard Diagnostic tool as well:
http://products.wdc.com/support/kb.ashx?id=cG8cVX
WD's Data Recovery Partners:
http://products.wdc.com/support/kb.ashx?id=sIB7SZ
Let me know how this goes,
D_Know_WD