Basically one of my springs popped out of place yesterday

, so i need a new one got quoted about £100 to have a new one fitted so i've decided to just get 4 new springs and lower the car.
Can anyone tell me some ideal springs to get, i've had a look on ebay and seen some jamex springs, are they any good?
Oh and how low should i go? I want it looking good but no rubbing at all with a full car. Will have 17" wheels on the car aswell if that helps.
Thanks.
