Thanks TIG - that's exactly what I was after. The existing tool that i found was 'sunview' within the SUNTOOLS 2.0 plugin, which also works.
pbacot - Here in Australia a lot of councils/jurisdictions will ask for these because traditional 'plan view' shadow diagrams arent particularly useful in winter when the sun is low, as the shadow may be on the ground but not necessarily overshadowing a wall or opening completely.
We also use it commonly for the available sunlight within multi level residential developments, as for each council there is a certain mandatory amount of sunlight required into a room for it to be considered habitable.
Thankyou all for your help, this is wonderful!