Hi there,
Yes, please have a search through the site, on this sub section and also in moving issues as I've commented quite a few times about it!
In short, yes, only a special, sought after, interesting, a classic USA car will be worth bringing over here. If you're car is a model of car that's considered 'bread and butter' then 'generally' it's not worth bringing and also if the same model is available here. If you pockets are deep enough, then of course do bring it !
Also, depending on where you ship from in the USA, the times quoted are quite far off. From the West Coast, it's a 21 day sailing time, and if from the East Coast, it'd be a 9 day sailing time.
Be aware that you'd also be liable to import taxes, VAT, a SVA test fee, and the cost of any modifications needed to make your car UK road legal.
I imported across a 2003 F150 Harley Davidson Anniversary Edition truck in 2004 when it was 9 months old and I do have a business contact who does this type of service.
if you'd like more information, including a quote etc then please let me know and can help you out.
Cheers, DtM! West London & Slough UK!