B&W G3, ATX and power boards

i just bought a cheap G3 350 logic board/mobo off ebay, for use with a mod project. Although I have to admit to the purchase being an impulse buy, so much so i didnt give much thought to the power supply, duh. So far, ebay UK (i live in the UK) is not turning up any B&W power supplies, but I've found a few in the US.

Using the stock power supply would of course be the easiest solution (and the most preferable as it also has the monitor power supply built into it, and for this mod I do want to have that option). So I got thinking about using an ATX power supply-I know absolutely nothing about using PC components such as this in a Mac, but I wanted to explore the possibilty of using a cheap supply, which I could potentially "go out and buy" at a shop (good grief!). However-I'd still like one with two power outputs, and the ones I've found actually seem to cost more than a B&W power supply shipped from the USA.

So. Does anyone out there have any good suggestions? (or maybe a spare B&W power supply?)

Also-I completely missed the power on/led board that this type of G3 uses. I wanted to ask-is this entirely neccessary? The LED I am not so concerned with, but I obviously would like to power up the mac somehow! If i was to use an old mac usb keyboard with a power button-would this power up the machine? Or, is it possible to fit the power on button from a beige G3? (???)

My main reason for moving to this model was a) it was cheap and b) I've had enough of my flakey beige G3 MT running Panther! I want better graphics, on board usb/adb/firewire and a faster bus speed.

Ok thanks.