The basics
Looks and handling mean everything to a hardcore Maxer. And one of the first mods we do to our cars is to lob out the stock shocks and sprins and replace them with pukka, uprated suspension.
The first headache is deciding whether to buy lowering springs or coilovers. Then you must decide which make to go for. And finally there's the little matter of price - the different kits covering a massive range in the readies department. All in all, it can be a bit of a nightmare.
But fear not, help is at hand. We will explain all that complicated suspension spiel; clarify the laws regarding MoT tests and lowering your car; and try to identify the correct suspension for you.

Aftermarket suspension doesn't directly affect you insurance premium, but  insurers can increase your premium for two reasons.
First off, if you live in a high-risk area and have fitted trick-looking coilovers like Spax's yellow RSX kit, insurers can see that as bait for thieving scum - so up goes your insurance. And if you've had special one-off suspension custom build for your car, the potential replacement costs are greater - so again, up goes your insurance.
This leaves you with a choice. Keep stock suspension fitted and don't risk increasing your premium, or be a man, take a hit and fit a monster set of coilovers, this reaping the benefits of superior handling.

MoT info
There is no definitive MoT ruling for or agains fitting aftermarket suspension, but your car will fail its test if the suspension fouls the motion or steering of the wheels. Contact between tyre and arch coused by an excessive drop in ride height will mean failure. And if your motor is slammed too low to even get on the testing ramp, that's an instant fail...and a complete waste of good money.
So, if your car is slammed 80mm on coilovers, crank up the ride height before the MoT test and you and your motor should be sorted.

Lowering Lingo  
Helper springs
Only found on coilovers, helper springs are designeld to prevent the main spring dislocating from the spring cup or top plate. Smaller and thinner than main springs, they are fully compressed at normal ride height. They offer extra spring travel for extreme conditions.

Progressively wound
Progressively wound springs have varied rates of compression to improve handling, the closer the coils, the harder the ride.

Coilovers are the hottest thing in suspension. They are complete spring and damper units which can be adjusted for a rock-hard ride and can sink the ride height lower than you dare go.
Dampers / shock absorbers
Without dampers your car would bounce down the road on its springs - Zebedee-style

Ride height
>This is determined as the distance between the chassis and ground. Fitting uprated suspension with lowering springs reduces ride height and can improve handling.

Damping rate
This determines the rate the rod moves up and down the damper body. The highter the damper rating, the stiffer the ride. Damping rate is adjusted either at the base or top of the damper.

Bump scrub
Bump scrub is the gut-wrenching noise you hear when a tyre hits the inner arch. This occurs when there is too much travel in the suspension.

Which way to go...  
Consumer X
Best option
Mr. X works and lives in a big town or city. He wants his hot-hatch to look low but is on a tight budget. His best option is to fit lowering springs. This will lower his car, but won't affect handling
Consumer Y
Commuting every day on B-roads means Mr. Y needs better handling to tackle the twisting roads faster. With a bit of spare cash he can afford to splash out on an adjustable damper and spring kit. Mr. Y can soften suspension for bumpy surfaces and stiffen it up for smooth ones.
full kit
Consumer Z
Driving on A-roads and track racing at weekends means Mr. Z requires a low, rock-hard ride. A steady income allows Mr. Z to buy a set of pukka coilovers for his motor.