This problem seem to crop up for me at least once a month at the same spot each time: I need to go straight on at a particular roundabout, but the majority of traffic will turn left. After experience, I found a lot of motorists just assume that cyclists are turning left too. My technique is to check behind me, make sure it's clear or that I know the motorist behind has seen me and then pull to the middle of the approach road (which splits into 2 lanes). But even doing this, I still find the odd motorist will overtake me on my right, then cut across me to go left. I suppose I could indicate, but as I'm not turning right, this could be misleading and at that point my speed is low, making me more unstable if I take a hand off the bike. Is there anything else I could do?