Cheapest and best do not go together very well unfortunately.
You can fit lowered springs and shocks, but my experience is that it's never quite how you want it and always end up with a slight nose up stance.
Better alternative is coilovers as you can adjust them where you want. As you've probably seen, these vary from £120 to £1200 (and probably more). The cheapest are pretty poor, give a bad ride and rust up. The most expensive ones are pretty much OTT for most people.
Good compromise is decent second hand set, or a set of mid-range, like AP.
On the cheaper end I actually found FK AK coilovers to give an acceptable ride, I ran them for 2 years and they were still fine and adjustable when I removed them, sold them on for £100 too.
As with all things, you pay for what you get. Phoning suppliers (DPM Performance / Demon Tweaks etc) and telling them you are a forum member you can sometimes get a discount that will beat the best price you can find on eBay etc.