Thanks for the comments all.

mudski, the 77 or P7 code is listed as F/INJ TF / B or Injection Pump injection timing control - which can be either air/contaminants in the fuel or the injector pump (or so I have been told).

Stumpie - I have either removed/replaced or wriggled that relay so many times it's not funny with no impact to the engine running!

yendor - agree and have worked really hard to ensure there are no leaks or air in the system. The fuel filter primer is really firm, and don't know how to check any other way. looking to possibly get a clear hose from the injector pump return or filter output to injector pump to see if there are any air bubbles.

joejtss - No stoppages for about 3 months after the relay replaced - only started to run rough and die after going up and down fairly steer ramps in a car park then didn't stop again until the other day (just ran like crap for a few days after removing the tank)!

threedogs - done pretty much all the rubber hoses - haven't replaced the metal fuel lines.

roofy - it gets driven almost every day and the fact the fault is so intermittent is the frustrating bit. Have driven it almost every day since the last incident for both short and medium trips with no issue!! Doesn't fill me with any confidence to go hit the tracks with it though. Was going to hit Landcruiser Park on saturday with my son (he also has an 03 Patrol - it just doesn't breakdown as he loves to inform me!!) but the last thing I want is to breakdown halfway up a hill out in the bush so looks like we'll just take his.

I agree with those that think it's a air in the fuel issue and will keep working to try and get it sorted, but there have also been a number of comments and also problems on other forum posts that are similar that wree resolved by replacing the injector pump- bloody expensive maybe though!

Cheers