On the bio vs. non-bio thing, keep in mind that the UK is one of the only markets that uses non-bio detergents. So if you are worried, remember that Tide and all the others in the US were bio, so it doesn't have to be as big a deal as people think it might be. I just avoid harsh additives like perfumes and colours.
I had trouble with our machine holding on to colours and found that it wasn't draining properly. Take a look at what splashes up during your final rinse. If the water is still looking pretty sudsy when it should be cleared, you may not be getting a good drain. Most brushes inside the machine only last a year or so and are an easy fix to make it drain better, sometimes other parts need more attention, but if it's an old machine, it may just need some TLC and will then work fine for you. Call a repairman--our last guy fixed everything for £30.