Compact Flourescent advice needed!

hey guys, iv just had a look at my lights, and theyr 150Watt 6400K CFL's, got two of them and theyr doing nicely for my plants, just thinking when it comes to flower i want to improve the light spectrum, i know i need warm white which is like 2400K or something, can anyone reccomend some UK websites to buy from, and how many is a good number, im thinking maybe 4?