Hi Falcon II!
Have you figured out what was causing the glow plug flashing problem?
Now that I have the same issue with a 2001 Mondeo 2.0 TDDI, I am having some huge trouble fixing it. It all happens when the glow plug light is starting to flash, the engine cuts out and it doesn't start again until it keeps flashing. I get the same P0335 and P1608 codes every time after the flashing light. The battery is also draining, I haven't figured out the cause of that either. All I know is that there is a short somewhere on the F2 Ignition Relay circuit, as I pulled the F2 fuse, the short has disappeared. Did you replace the K41 Ignition Relay or the K115 Battery Saver Relay?
What about the flashing glow plug light, have you actually found the cause of it?
I would really appreciate your help. Thanks!