As for all that crud you can see when you took the sump off.I would use paraffin soaked rags and an old tooth brush to remove all that you can get at,and do the same to the sump pan itself.Then chuck some cheapo oil in there and run the engine for a while,then drain it and refill with the good stuff.
For what its worth,imo your going he right way about this.Systematically and methodically.Not cutting any corners.Your engine should run as sweet a nut when your finished. 
+1

Camshaft sprocket to camshaft 50 + 60° + 15° 1
That is correct-just ignore the 1 everything else is correct
Many thanks

That looks like someones oven after a good turkey roast 
LOL

I now have another problem

although I think I've sorted it but would like to run it by those who know

Put cam belt on as per the DVD, (not as simple to a novice as the DVD shows

) Got bottom lines in the right place worked upto cam 1 & 2 & got them in the right place, then realised it was on backwards! re did it again and moved on to cam 3, the line was short of the mark by a good inch

went back and re checked everything and was ok so took it off again and compared it to the belt that had come off, both have same GM code number & all the line in the same place
Refitted all around ignoring marks on 3 & 4 cams only to have too much tension to put the roller in place, whereas on the driver side there was quite a bit of slack. So I removed the wedge and moved the belt towards the passenger side which enabled me to fit the roller.
The pictures below show how it is at night fall!

Cams 1 & 2 lined up with cam belt & cover marks

Cam 3 lined up with cover belt way off

Cam 4 lined up with cover as cam 3


Bottom line a tooth towards Cams 3&4 TDC lines up with cutout in cover
Have I done something wrong, or is it that the layout of the 2.6 is slightly different to the 2.5?