Poor/no road markings to establish if single or dual lane

There is an issue with the curbridge road roundabout which meets deer park road and thorney leys road. despite there being no visible road markings to suggest the roundabout has two lanes, drivers are using the roundabout in that manner, and despite the fact i am indicating to turn right, if there is enough room cars will undertake me causing near collisions. the same occurs with cars overtaking at the give way or on the roundabout. Due to the road markings and the highway code i am not assuming that there is two lanes just because there is room but i am encountering near misses from car drivers as a result. I would like clarification of the highway rule by either painting lanes to show all that this is the case, or signage displaying single lane to show all that this is the case. Thanks, Lee