To do the job correctly you want to fit a KM/H to MPH converter, fitting the correct one will take out the 112mph limiter and obvously the car will read in MPH then, fit a rear fog light, I would not drill into the bumper or bolt on the silly looking one that attaches to the bottom of the bumper, just convert the drivers side reverse light. I have a very neat install on mine that lets me swap the reverse light for a fog light at any time, it does not affect the "bulb out" warning light on the speedo cluster either.
Also the radio either needs swpped out for a UK one so you get the correct channels and it reads correctly, either that or you add a "band expander" to the JDM radio. In Japan radios are made to receive in the 76Mhz to 90Mhz band, but in other countries you need as much as 108Mhz, so by fitting the band expander you receive the UK FM channels but this means your stations read differently, for example, if you want 98.3FM you have to put in 86.3 if using a 12mhz unit. Japanese radios dont have RDS either.
Here in N.Ireland another rule for MOT is that, the speedo must have a dual display ie MPH & KM/H.