Brought a C7 in from the US 2 years ago. Costs were*
1. Price of Car in GBP
2. Shipping costs to get car to UK port including Marine Insurance (approx £2,300 with Hill Shipping) - This included shipping from dealership in the US to the port
3. Add Import duty of 10% onto the above sum
4. Add VAT at 20% onto total of 1+2+3
5. IVA costs and first registration fee.
* Shipping costs have increased at present.
All in this was approx 38% of the cost of the car in GBP. Exchange rate is slightly better at the moment, but as a guide I would say whatever the price of the car is in USD will be the price of the car landed in the UK unregistered and unconverted.
IVA costs were limited to the application fee (I believe this was approx £95 or so), installation of rear fog lamps (US models have no rear fog lamp but two reversing lamps), installation of side repeater indicators (again none on US models).
This is where I spent more than most as I wanted to try and get a "factory look" rather than lights bolted on everywhere. So the mirrors were swapped out for Euro spec mirrors (obtained through Keith at Eurovettes), wired into the wiring loom properly (the US wiring loom does not include the wiring for side repeaters), and replaced factory rear reflectors with modified reflectors containing LED's for fog lamps (no unsightly bolt on rear fog lights). I believe others have converted one of the reversing laps to a fog lamp similar to the Euro Spec cars. Note there is no wiring for rear fog lamp or dashboard switch like the Euro models have.
Cost of this work was around £2,500 in addition to above.
Not sure where you have found a £29,000 C7 from, looking at prices at the moment in the US they seem to have gone barmy. As far as I can see anything at that price is either very high mileage or on a rebuilt/salvage title.
Jason