Ben I know that you don't want to put anymore money into the car but a proper map is not all about power its about getting a nice reliable power and torque curve this can be achieved still maintaining the lower numbers, when I had mine mapped it was making way past 270 bhp but Matt Thorne ME Motorsport who mapped mine advised that with what I had fitted at the time 250 bhp and 230 ftlbs was enough safe and he tuned a lovely flat torque curve in mine so no big rush just steady stream of very usable power almost like a large normally aspirated engine .
I think that will be the making of your car and if you have the motor reasonable the mapping may not be that bad talk to Skuzzle or ME Motorsport.
I'm defiantly getting mine remapped once I get it back up and running as I have new bigger injectors 650cc Bosch, Skunk2 inlet manifold and up-rated turbo plus of course a full rebuild and full forging. I'm using the same ME221 ECU so I can adjust the settings for the bigger injectors but the professionals really are worth using.
I think you would be very very surprised the difference a visit to a good tuner and a rolling road can make, Plus you can show the map to prospective customers so they really know what they are getting.