The Gelish system uses either a special LED lamp or a 36 watt UV Lamp. Nail Harmony UK supply both versions which have different price points. I don't believe a LED lamp will cure any other gel products as the LED lamp sold by Nail Harmony is specific for the Gelish system.
UV lamps are more versatile and MAY work with more than one system. It is best to speak to the experts (CND/SweetSquared, Nail Harmony etc) and get the full specifications of their lamps. Some people claim their UV lamp works with all systems and the product appears to cure correctly but clients may come across issues later on.
Hope this helps.
NAILS BY METShttp://blog.nailsbymets.comhttp://twitter.com/NAILSBYMETS