You don't need zoom for macro shots. It's not how they work
You just need a relatively small focussing distance for macro shots. Even then, you'll only need it for spiderlings. Leon uses a Canon A80 (discontinued) for his Tarantula shots, and produces some fantastic results. I'd recommend something like:
Canon Powershot A620 - 7.1 Mega Pixel. 1cm focussing distance in marco mode. £199.99.
Read the review on Steve's Digicams and see what you think
Seems pretty good, especially for the money:
"The A620's Macro (close-up) capabilities are superb, allowing you to focus as close as 0.4 inches (1cm) from the lens. When shooting subjects at such a close range, it is very important that the camera controls its flash well to ensure you don't over exposure the subject. The A620 does just that, "throttling down" if flash for near perfect exposure ever time. " Sounds spot on