That Focus is group 6.
BUT...
Group 6 doesn't mean more to insure than Group 5...
It's quite a puzzling system, but actuaries spend years working this kind of stuff out.
Cars have an initial grouping based on their performance and intrinsic value. Diesels are slow (though a 1.8TDCi is a good 10s - putting it quicker than all but a 1.6 Saxo) so the group is lower than the equivalent petrol engine. They're slightly more expensive to buy, but not enough to affect the grouping.
The grouping is then modified by several factors, according to how much risk those factors are worth to the insurance company - or rather how much those factors make it more or less likely that, instead of making money from you, they have to give money to you...
The owner
1. Gender. Males crash more than females (or at least they crash harder, more than females). Males represent a higher risk, so the modifier is higher.
2. Age. Under 20s and over 80s crash more often than any other group. Modifiers are higher for these groups.
3. Profession. Low paid manual and very high paid professional people crash more often (I make no claims as to the reasons why), so modifiers are higher for these groups.
4. Endorsements. The more driving offences you have, the more likely you are to drive above the law/your ability.
5. Accidents. The more accidents you have, the more of a liability you are.
6. No Claims Bonus. The longer your period without claiming against your insurance, the less of a risk you are. "Full" (5 years) NCB represents between 50 and 75% saving on your premium.
The vehicle use
1. Overnight/daytime location. Vehicle is less likely to be stolen or damaged from in a garage than on your drive, and less likely from your drive than from the street.
2. Use. Drive it for leisure only and you're not often in a position to crash into something else. Commute and you're on the road at the same time as everyone else...
3. Vehicle security. Opportunists won't bother with an immobilised/alarmed car, reducing the risk to the insurers of having to pay out.
4. Cover options. Third party only means they only have to give money to repair the car you hit, and represents a lower risk than having to pay for your car as well. However, if your car is worth both halves of sod all, Third Party only can represent a much higher risk than Comprehensive insurance - so don't assume that TP/TPFT cover is always cheaper.
The car itself
This is the biggie that few people ever consider.
The typical crash is an offset front-end vehicle/vehicle collision at 30-35mph . As you've seen earlier, the Saxo/106 don't behave very well in this situation, so the insurers will end up not only paying for your car and the car that gets hit (assuming it's your fault), but also for medical and loss of earnings expenses for the occupants - possibly even death. Bigger - and newer - cars behave better, so the likelihood that the occupants will need any medical attention or time off work decreases, decreasing the risk to the insurers.
Typical repair costs are also factored in. Ford parts are cheaper than PSA parts, and you're likely to need less of them (and some time on the jig) because the car doesn't just disintegrate - the survival cell is still intact, for example.
There's also the typical crash involving that vehicle... Because the usual owner of a Saxo/106 is a teenage girl or boy, the typical Saxopug crash is a high-speed, showing-off-to-mates affair, involving a complete write-off and multiple occupant injuries - and legal action from the other car they mullered. This costs insurers quite a bit. Your typical Focus diesel driver is an old biffer who goes down the shops of a Thursday, covers a mile a month and does the IAM-shuffle. The typical accident in a Focus diesel is a side-scrape with another car he didn't see in his mirrors, requiring a quick panel beat and respray for £140.
Factor in the value of the car (£5k for the 3-year old Focus, £7k for a new C2 - less money for the insurers to pay for a suitable replacement in the event of a write-off) and don't forget to precisely calculate how far you travel in a year (less than 7,000 miles gives you one hell of a discount compared to 10,000 miles+ - less distance = less time exposed to danger).
Get a quote from Confused.com for a Focus TDCi and a C2 1.4 for a new-ish driver. If the Focus isn't cheaper in most cases I'll... do something. Maybe. But I'd be very surprised.
Volvos mite be big but ur alot safer in one that ur city cars 
