Thanks for your comment, although that's not really the issue. The reason I am doing it in MDX is that the client needs to analyze the data dynamically and won't be using SSRS for static reporting, otherwise yes I would do it in SSRS. I included the MDX above for completeness.

The actual issue is that there is an integer value which is correct at source but when processed in SSAS at certain hierarchical levels (always 2 out of however many for some reason) is showing as a large negative value before any of the MDX above is applied.

If you could share your thoughts on that I would be grateful 🙂