Joe
Question #1: Do dealers sell from their stock, or, do they order them?
In UK, mainly they have a few in stock (not many) plus demos and showroom display. Cars are often factory order (10-12 weeks) or sold from pipeline in transit. Manufacturers (in general) only allow car dealers to order cars with named customers against them. Or else the richer dealer groups would suck all supply and create gluts of cars. It's generally a fair system, although people always moan.
Question #2: How many cars does a typical dealer have in stock, ready for sale?
New cars? Very few. Maybe they have one or two. Plus demos etc. Plus they may have arranged a few pre-reg cars (but these are no longer new, they are registered - eg to the dealership or a fleet company).
Question #3: Do shoppers want to see the car they're going to buy before they buy that car?
New car? The actual new car? No.... they are happy to see a showroom display example. And if at a dealer, to test drive a similar demo model. From me, they only see pictures and the manufacturer website, but of course they know what they are getting. Customers see hundreds on the road, in the supermarket car park, etc etc.
Question #4: How do shoppers in the UK dispose of their old car?
The part-exchange. In the UK, commonly the dealer will buy it, but more and more often these days people dispose privately (as they get a better deal, eg through AutoTrader, Ebay) or use an online service like Sell My Car at webuyanycar.com - Free Instant Car Valuation
Question #5: Can you describe the brokerage network that allows you to sell any car (this concept is foreign to us)
I exist. I find customers for brand new cars, they visit my website. I advertise lease (eg contract hire, operational lease, PCP) rates on virtually every available brand new car. Some are good, some are bad. They go up and down like prostitute knickers, nature of the industry. That's basically what I do. I advertise clear monthly rates.
I have about 300-400 people (and businesses) apply every month. I find the most advantageous deal for them (and me), and propose them to finance down whichever route (eg a dealer). They pass or fail. If pass, they sign an order form with me and the dealer orders the car (based on MY WORD - so I may have several £million of cars on order with many different dealers with no money down, just based on trust). Sometimes I may order via another broker who has more advantageous terms than me.
I am sent the lease paperwork by email, and I send this to customer and get it signed, then posted back to me. I send this to supplier and from them to finance company. Then, the brand new car is delivered to the customer (usually driven). The customer has never previously seen the actual car, although they know what they are getting. This is consumer goods stuff, like a fridge or washing machine.
Average time is about 40 days. Some much longer (ie. Jag XE now taking orders for next May). Some much shorter (there may be a batch of physical cars and then I can turn around in 2-weeks).
I invoice supplier for commission.
Therefore, I can obtain and supply any new make/model. But I avoid silly ones (ie high-end) where a cancellation may mean an expensive embarrassing unsold unit. So most of my cars are unsexy standard stuff 
I like common cars that I can resell if there is an issue during the lead period (eg customer loses their job, etc).
So, I have several hundred customers in process at any time, using my super LINGO system (no dealer can communicate like me) chatting about their new car for 40 days, having fun, uploading, downloading, being entertained and waiting for their new car. Going through my sausage machine (but very personal) process. All communication is transcribed and average reply time is less that 5 minutes during working hours.
The above is possible because the geography/size of the UK allows me to deliver anywhere, plus one law applies (no state laws) and everyone speaks English. UK is a mature society. EU competition law is a great help in preventing unfair cartels or restrictive practices.
Hope that helps
Ling
