The C03 error indicates that the timer button is stuck or not responding. Check if the buttons can move freely; you may need to remove the rubber cover by prying it up. If the buttons move freely, sometimes the error can be cleared by unplugging the oven (or turning the unit off at the circuit breaker) for several minutes (up to 30 minutes). Turn the power back on. Then press and hold the Timer button for more than 180 seconds (3 minutes). Some people have reset the timer by setting the function selector to "interior light on" instead of pressing and holding the timer button.
If none of these actions work, then the timer clock needs to be replaced. If you add a comment with the full model number of your oven, I may be able to give you the part number. NEFF doesn't list a B1322.1; there are several B1322N1 models. There will be addition numbers in the model number and there may be some extra letters as well. See http://www.neff.co.uk/store/spare-parts
to get a picture of where the rating plate is for your unit. That will have the full model number.
I hope this helps.