Here's how roundabouts should be handled, according to the UK Highway Code.
When taking the first exit to the left, unless signs or markings indicate otherwise
• signal left and approach in the left-hand lane
• keep to the left on the roundabout and continue signalling left to leave.
When taking an exit to the right or going full circle, unless signs or markings indicate otherwise
• signal right and approach in the right-hand lane
• keep to the right on the roundabout until you need to change lanes to exit the roundabout
• signal left after you have passed the exit before the one you want.
When taking any intermediate exit, unless signs or markings indicate otherwise
• select the appropriate lane on approach to and on the roundabout
• you should not normally need to signal on approach
• stay in this lane until you need to alter course to exit the roundabout
• signal left after you have passed the exit before the one you want.
When there are more than three lanes at the entrance to a roundabout, use the most appropriate lane on approach and through it.
For some reason this doesn't work in Argentina where, as you all know, it's a free for all.