• yes, you are right, that is absolutely the case that VS is using my local client account and SSRS is using its own User account. It does appear that User Permissions is the answer but it could be a red-herring because the Stored Procedure has changed but it still exists as before and the permissions on that SP have not changed.

    It's a weird one which has our whole team stumped 🙂

    Your input is much appreciated however, keep it up 🙂