Custom and practise

[darcey84]

we have been carrying out tasks at work that is neither in our grading matrix or employment contract. We started doing these tasks mostly out of goodwill to our clients and employers. We have now withdrawn these tasks in order to negotiate a higher grade which would reflect the new working practices, however our employer says that if we do then we would be in breach of contact as these tasks have now become custom and practice and therefore implied into our terms of contract. Is this legal? Custom and practice see taken for granted!

[factor-fiction]

I have seen this question of yours (with some answers) elsewhere but i can't find it now. Can you remind me where it was? Ta