You answered your own question. You need to go to other time frames to avoid high spread costs at 0000UTC. One method is to test and develop a strategy on daily charts and then adapt it to simulate daily candles from say 0800 to 0800 and then use these for your trade entry conditions. It means you have a lot less data to back test on but then if it worked on daily candles and then still works on your simulated daily candles then you have some confidence that it is a robust system. A kind of IS and OOS test using a different time of day as the start point.