I run a clothing business which sells items as individual pieces (know as seperates) but as well as "sets" - which is a combo of those individual pieces.
I have the "individual" pieces as a configurable items, with Size and Colour as the attributes.
Id like to "join" two configurable products on one product page so they can choose colour and size for two items
Has anyone got any ideas using out of the box magento or mod or extension ?
Let me know if you need any clarification
If I understand correctly, you want to create a Grouped Product using Configurable Products. To my knowledge, this is not currently possible in Magento core. Grouped products are designed to consist of simple products (without custom options).
There are extensions for this. I have not used this one, so I cannot vouch for it, but it seems to meet your needs: http://www.magentocommerce.com/magento-connect/grouped-options.html
A work-around might be to create a Grouped Product for each size/color simple product. But the frontend might look confusing to the customer... i.e. There would be a list of Small-Red Shirt, Small-Blue Shirt, and so on. Possibly some modifcations to your theme might make it look less confusing to customers.
Hope this helps!