Sounds a bit like me. A couple turned up in Keele student Union looking for Ace machines. I watched them for a while as they were being fairly obvious about exchanging everything for the lines. Paid them £40 for the list of emptier programmes and we teamed up for a while as I had a car, but they were pretty pikey and we didn't really get on!
After then I had limited success with stuff like Donkey Kong, Bling King Crazy and DOND WIYB but basically focused on my actual job(s). It all got too competitive, and when the machines got hooked up to the internet most manipulations didn't last more than a few weeks, unlike the Ace thing that was live for well over a year.