Are they definitely battered? Sorry to keep pushing the point but... I've dealt with 6 MX-5s, all of similar age to yours, and never seen a dead wishbone bushing on any of them (drop links / ARBs yes, but not wishbones). it is of course possible but it's worth checking before going ahead and repalcing IMO.
The Flo Flex ones are... bluntly... crap. People say they are good because they make the car 'feel' lively and fast, but a good friend of mine fitted some to his race car and they were squeaky, induced binding into the suspension and generally nasty. He swapped them for IL and the car has been completely transformed.
Again, sorry to bang on, but just trying to save you the cost of a wasted set of bushings and a full geo...