Check that it really is a Lotus Carlton. There are quite a few replicas around, and these aren't worth the price of a tank of petrol. Check the chassis number starts with SCC000019, and that the log book agrees. Check that there is a Limited Edition badge on the passenger glove-box, and that it shows the cars construction number. Valid construction numbers are 0001 to 0950. Also check that this agrees with the identification plate under the bonnet, where the C/n should be followed by the letter 'G', indicating it's a UK spec car, or 'D' for a German spec car. Take a look at James Waddington's web site for a good description of what the ID panel information means, together with a list of the other possible country designators.

Check that the car has been serviced regularly, preferably by one of the 16 approved LC dealers. In particular, check that the intercooler water impeller has been changed. Apparently these can break causing the water in the intercooler to boil and break it. I don't know anyone that this has happened to, but I have heard stories.

Make sure the car uses the correct oil. It should be Elf Competition 20W50. Some owners have started to use newer synthetic oils like Castrol RS and Mobil F1. But the bloke at Lotus says these are too thin, and that this is what can lead to the turbo failures.

UPDATE : Vauxhall have now run out of this special oil, and will now try to sell you standard Mobil 1 0W40. Others will disagree, but my opinion is that this is far too thin. I have switched to using Mobil 1 Competition 15W50, which is a fully synthetic oil available from most larger garages, including Halfords.  I know others are using Silcolene 20W50.

Brake disks wear out, as do the pads. New front disks are 32mm thick (minimum permissible is 30.67mm), and cost £613. New rear disks are 22.9mm thick (minimum permissible is 21.84mm) and also cost £613. Front pads are 21mm thick (minimum permissible is 7mm incl. lining plate) cost £300+ from Vauxhall, or £100 from other sources. Rear pads are 17mm thick (minimum permissible is 6.5mm incl. lining plate), and are £100+ from Vauxhall, or £25+ from other sources. Take a micrometer/ruler with you and try to measure all these on the car you are thinking of  buying. As you can see, replacing the whole brake system will cost you £2000. Also check for corrosion on the brake caliper pistons. This is very common, but not too serious. Ignore what Vauxhall say - the calipers can be reworked for about £50-£100 each.

Check the front and rear wheel arches for rust. The body kit covers most of the metal parts of the door sills so it is very difficult to check here - and that's where the rust starts ! Also check the boot floor and under the bonnet for signs of accident damage.

Check the front spoiler and rear bumper for cracks. Don't worry too much about stone chips on the spoiler, you can always get it re-sprayed. Every car gets about a dozen new chips per mile. What you are looking for is cracks, because if the damage is irreparable, you will have to replace it, and these plastic panels are £1500 each,  that's if Vauxhall can find one to sell you.

Check the front and rear tyre condition. The fronts are 235-45-ZR17's, and will cost you between £100-£170 each, depending on the brand. The rears are 265-40-ZR17's, and will cost between £150-£220 depending on the brand. So if you have to buy '4 new boots' , you could be looking at the thick end of £800. In my opinion, the brand doesn't matter, although Vauxhall & Lotus insist you use the Good Year Eagle (Not the F1), which I have found impossible to source recently.

Check the front and rear rims for damage as they are expensive to replace if you want a 'showroom condition' car. If you come across a car without the correct Ronal 5 spoke alloys, be very suspicious. If the seller tries to tell you they 'prefer the look of Brand X alloys to the originals' , tell them they are a Pratt. In any case, knock £2 grand off the asking price, and consider walking away (unless she is a stunner, when you should tell her that you are a psychiatrist, and offer her free therapy.)

Try not to buy a chipped car - or one that has been chipped in the past. You don't need 500,550 or 600 BHP on the road. And you certainly don't need to buy a new engine, gearbox, differential and driveshafts when they break - and they will. I'm not just being a sour-pus. All the reasons why you shouldn't touch a chipped car with a barge pole are described here