The short answer is yes, your problem could've have resulted from your cambelt change, but it depends on how your garage did the job. The valve and base injection timing and tension of the belt is critical, and there is only one correct method of doing it. Specialist tools must be used to lock the crankshaft and the camshaft in their exact positions when fitting a new belt. In addition the camshaft pulley must be slackened by loosening the three bolts that secure it to the camshaft which will allow the pulley to move freely on the shaft, and only re-torqued when the correct belt tension is achieved with the locking tools in place. This will ensure that the crankshaft, camshaft and belt tension are all correct, and most importantly the base injection timing will also be correct. The locking tools should then be removed and the engine turned in the direction of normal rotation for at least two complete turns, and in multiples of two turns. The locking tools should then be re-fitted, and will easily do so if both the crankshaft and camshaft line up, and the belt tension should also be correct.

The incorrect way to do it is to mark the pulleys and an adjacent spot with paint and replace the belt. This method will not ensure the correct timing, or even the correct belt tension. The base injection timing will almost certainly be wrong, and if it's outside of its limits then a fault code will be generated and your traction control lamp may be on. Since you say the fault occurred on your way home from the garage immediately after the job was done you would be forgiven for thinking that they didn't do the cambelt change properly, and may even have been unaware of the correct method of doing it. You could remove the upper timing cover (it's easy to do) and check to see if there are any fresh spots of paint on the camshaft pulley. If there are then it's a good bet that they didn't lock the shafts and that the timing is wrong......

Can,t see it being related to a cambelt change.Surely an 05 tdi is a Pd engine that does not have a timed injection pump?

You're right, it doesn't have a timed injection pump as such. Instead they have unit injectors that are operated by seperate lobes on the camshaft. The base timing can be altered in much the same way as a conventional pump, and it's essential that the camshaft is locked in the correct position when replacing the belt by using the locking pin. If you don't then the base timing could be either slightly advanced or retarded, and as we all know the slightest adjustment will make a big difference. If the error is too great a timing deviation code will be set, and the traction control will not operate.....