In reply to AdrianC:
Napisan is OK, but it seems to kill elastic, though I've no hard evidence for this, which is not great for lycra sports gear. We've found Milton fabric much kinder to elastic. Seems to work just as effectively.
http://www.milton-tm.com/antibacterial_fabric_solution.html
You used to be able to get it in Tesco and Sainsubury, but now don't seem to get it there. We buy it online - 3 bottles at a time, which seems to last a good long while - months and months.
Its safe on Wool too.
You can also get special washing soaps, but these are not safe of wool, and as most sports washes seem to have wool socks in our house it would be a pain to do separate washes just for cottons and synthetics as well as darks and whites...