Oh, and Wammers, you were right about the cheapo tool. The £15 Fleabay tool bent on the first attempt although in its defence, after straightening and some fairly brutal hammering, it was useful in getting the viscous fan off and more importantly in holding the water-pump still while I torqued up the pulley bolts on reassembly.
If only you'd posted that advice before I'd received it!
If only you'd posted that advice before I'd received it!