Lowering the body to the road, lowers the centre of gravity which does increase the cornering ability but the tie rods(steering arms) and the lower control arms end up on funky upward angles where they were once almost square. This places load on the ball joints of these particular parts which they are not designed to sustain. The steering becomes heavy and the parts deteriorate rapidly. This increases sloppiness in the steering and bump steer.
Roll centre adjusters (RCA's) are spacers used between the strut leg and the lower control arm to correct this problem.
Next you have the issue of increased negative camber, where the top of the front wheels tend to lean inwards. Generally a positive trait on a track car and for the fan boys who love to chew through tyres, but the tread doesn't run squarely on the road, increasing tyre wear on the inside line and decreasing forward traction & braking capacity. Also increases bump steer. You use adjustable camber tops (strut tops) to counter this issue, although most wouldn't consider it one.
Finally you have shock absorbers. Short stroke shocks are required to keep lowered spring trapped inside the strut itself. The standard shock absorbers upward travel is big enough it will allow the lowered spring to fly free of its upper and lower enclosure. These shocks are not generally of the shelf items and extensive part cross referencing is required to find the right shock and then you generally have to modify the strut to fit it.
It's generally illegal to do for Provisional licence holders. It is definitely a lot more complicated than most people expect and the detriments out way the style points 9 times out 10 unless you do the job properly.
Just do the 30mm springs in the front with 35mm RCA's (available through Techno Toy Tuning or others) with standard shocks and get a wheel alignment. Then use inch and a half blocks in the rear with Nolathane or Super Pro bushings. It will be cool.