Are you recommending that someone who has confessed to not having much knowledge about cars should go to a trade auction to pick up a family motor? I've been to numerous auctions, and I've still managed to get stung on a few due to unseen faults, I've seen people get over excited and bid far more than they had planned to.
Apologies if it came across like I'm criticising you 2 Sheds, that wasn't my intention.
Car supermarkets as a rule (I'm not talking about independant dealers) buy cars cheap from fleet companies, spend an absolute minimum on recon. and make their margin on finance & insurance packages. There are of course exceptions to the rule, and if a local place has a good reputation and a thriving business then I'm sure it's deserved.
My point about going to a dealer is that you've got a point to escalate any problems via the manufacturer. Also warranties from reputable sources in general are quite good - if you're familiar with the FSA's regulations you would know that these companies can't refuse payouts if it's a valid claim. The problem with a lot of aftermarket warranties is the list of exclusions - Manufacturers warranties tend to be far more comprehensive. If a main dealer receives a car for work which is covered by warranty, then they will obviously process it as such - they get paid by the warranty supplier, customer satisfaction is greater= more chance of repeat custom in the future.
My point about low mileage valuations was aimed at buyers for the trade, a car may be more desirable if it has lower than average mileage, but they wouldn't necessarily pay a substantial amount more for it (although they will of course try and charge more for it!). Same as everything the world over, an item is only worth what someone will pay for it.
As you know, you can check a car over and over until your blue in the face, but that doesn't mean it's still going to be fine in 6 months. Things go wrong with cars - that much is a fact. The Zafira is however as sound a car as any, not without it's niggles/problems but then as you rightly pointed out, similar could be said for any car that you have knowledge about.
What an in depth discussion on cars for a carpet cleaning forum..

Ash