It would be quite difficult for you. Jez has yet to do an S15 map for a chip. Its not a problem to do it. Its just a case of getting a subject S15 with stage 1 or 2 mods and mapping it. Then he's got a template. Then you'd have to make sure you're running the same octane rated fuel...
However, getting a subject S15 to start with is a problem in the UK. Most people aren't bothered (though they should be) or go the Emanage or PFC route.
I can't guarantee that the chip could be manipulated as well is a PFC, as i don't know exactly what can be done with the chip.
You can either send an ECU to Jez or order a chip and install it yourself (instructions are on his site). This would be once he's got a map...
Maybe one of the UK people can be convinced to go and see him...
A lot of the S14/a owners on SXOC run a Horsham chip with good results. Basically, you will get a nice smooth and consistent power curve with the relevant stage mods. There are some dyno graphs on his site...