Happy days mate
You've learned a valuable lesson in sensors, like I said previously. Never automatically assume that just because a new sensor is fitted, it must be working.
Don't feel down though, I know it has been a hassle but after all that, it was a simple item in the end.... look on the bright side though
All the checks, stripping down and cleaning relays, earth points and glow plugs means you have eliminated any future issues for a long, long time so time and money well spent...
Now go out and enjoy the bloody car like it was meant to
Don't forget to give it an Italian tune up with it been standing, Take it for a jaunt down a motorway in 4th gear at 60-70 mph without booting it, just constant revs for 15-20 miles. Then all that wetness from fuel sticking to old carbon deposits will have burnt off and the car will be happy, happy, happy