Hi,
Okay - now we're getting somewhere.
It is best to only use OE service parts, as the difference in cost is relatively so small you might as well use the parts that are specifically made for these cars.
I would also only recommend using only OE sensors when replacing. They are usually substantially more expensive, but you'll only need to do the job once, so in my book it's worth spending more on the item and only paying one labour charge.
As for the current issue, I would suspect you have a failed crankshaft sensor.
Some generic fault code readers do NOT pick up the fault code for this failed sensor.
It would be wise to ask any garage who is going to work on your car if they use VCDS. If they say yes, ask them to perform a full scan and provide the print-out. If they don't use VCDS, perhaps it's best to find a garage that does use this tool.
If you venture along to any of the social events this club runs (a great fun day out whatever social you go to), many of us have the VCDS tool and will happily scan your car free of charge and explain any issues you might have
I'll see if I can locate any previous threads about crankshaft sensor failure/replacement for you
Edit:
Here is one thread but the pictures are missing, however this should explain the method used to fix the problem:
http://www.a2oc.net/forum/showthread.php?9768-Poor-starting-cure-Crankshaft-sensor-replacement
Cheers
Jeff