I really like the idea of making some balloon decorations for friends/family, are the qualatex/sempertex round balloons useful for this, or are they too thick? What kind of balloons would you use and where might I find more information on this subject?

These are the right ones. Depending on type of decoration. 11inch seems popular for many but I am sure others with more experience will guide you here. If you do a search you will find many tips on decor, including the infamous ikea lamp! (Trust me, search it)

Thanks, I guess any tall thin up light would do the job? Not that I know what the job is yet! So are none of the balloon columns freestanding then?

It is possible to make small columns without poles. Here is one example that uses a 646q as the central column. If you do a quick search on here you will see better examples by others.