Ditto what Charles said.
Check out
http://www.import-car.info/modifications.shtml
Specifucally some items of concern may be
* Rear indicators are separate to the brake lights and the right colour (this is different to US cars)
* Front indicators are the right colour and have repeaters on the side of the vehicle. This may require small indicators added to the side of the car and holes drilled in the wing as appropriate to accommodate them.
* A red rear fog light is fitted - US cars often don't have these.
* The correct white parking lights are present.
* Headlights are pointing the right way - check before you bring the car in that this does not mean a costly set of new headlights!
* Tyres match the advertised top speed of the vehicle. Tyres have a code (R, S or T rating) on them which matches a theoretical top speed. If the rating is lower than the manufactirers advertised top speed - you'll need new tyres (for the SVA anyway!)
* The speedometer has Kilometer as well as Mile readings.
* The right brake fluid level indicator is present on the dashboard or else the reservoir is clear.
* The number plate meets UK standards (correct size, shape, lettering)
* Protrusion standards are met (ie removing long exhaust pipes, bull bars, mascots etc)
You really need to find out it they apply to your year or if you are excluded. The site has some contact information as well. Good luck