thanks for your help tullio, Im aware that the canon branded tele's and WA's etc are all 58... on the lensemate site the best proforming tele is the raynox dcr1540pro which is a 52mm lens. The best proforming WA is the raynox dcr720....which is also a 52mm jobbie. So there is no real worries about getting good quality lenses.
What i was more interested in was whether there was any noticable difference between using a 52 compared to using a 58. whether the 52 was more prone to vigneting etc.
The availability of lenses and filters is just about even between 58 and 52mm but the 52's seem a smidgen cheaper.