Gear doesn't give you the right to charge £600 - your overall service and presentation 100% does.
Most of the mobile guys I know are on that kind of money, it's who you market yourself at.
If you're just getting back into it now, this is the time to aim high, much harder to go from a back room in a pub at £100 to the good stuff.
Gear does play a small part, don't turn up with LED dots everywhere and a soundlab sound system and you're half way there.
I would say 90% of DJs across the country the use some form of LED Lighting. It's pretty hard to disregard nowadays, it's light, no duty cycle's, the effects are improving weekly (some say much better than traditional lighting), and the price is so much better than traditional lighting. The key is to mix it with something else such traditional halogen fixtures/uplighters/lasers/starcloths etc etc. I haven't sold a halogen fixture for about 18months, and they where b-stocks just going cheap.
The problem with dots everywhere is venue's not allowing (or dj's not using) a smoke/haze machine to get the best from the lighting looking towards it, not away from it on the walls/floor. A halogen fixture just throws out dots everywhere, unless it's got gobo's in, but scan/barrel and moving head LED fixtures come with Gobo's in now. As do some lasers.
Not every dj has a grand to buy a single Martin Wizard, plus it's pretty pointless runing it on S2L. Most DJs don;t run DMX. Master Slave on S2L is about as far as most go.
Advertising yourself wise I'd go straight in, offer a gig for free to see what they think. Do you offer Karaoke? This a massive thing for most pubs nowadays, some in our area do Karaoke Thurs through Sun night.
Get a website up, you should be able to hit the top of page 1 with minimal effort for say ''mobile disco + your town''. Maybe do some Adwords on a small budget if you want to go further afield and cover your county.
Don't price yourself too cheap. As much as people want a bargain (and there is many who want a £100 disco) there are just as many who
expect to pay more. Pub work £100-150 is about the norm. Weddings £250+. The rest decide how much effort your going to put in. If your going to go to meet customers, gather playlists from them, invest in extra lighting or better equipment etc etc.. make sure you charge for it.
Main way to look at things is do I want to be out every Friday night for £100, or would it better to do once a fortnight for £200.