The reason the rear tyres was rubbing is due to the GTR having a completely different offset to the GTS-T. You can fit plenty wide tyres in the guards with the correct offset, but the GTR offset is not what you want.
As for the dimmer switch, its for the dash lights only not the headlights, and can be done quite proffessionally. Mine had one added as part of compliance and you can't tell it from a factory job.
And Angus is comment is wrong, there is certain stipulations about a car having to go over Dickson even if it has been registered elsewhere. This use to be all imports and all cars 10 years or older. Worth double checking the exact rules at the moment.