I am not a biker, but basically if your actions affect another road user, then the examiner will mark either a serious or dangerous error. From what you say in your post, the examiner detected the cyclists slowing as you turned across them. If that is the case then your actions would be marked as either serious or dangerous.
gilmore1988 wrote: i feel the cyclist would have acted like that weather i pulled along side saw the junction and then decided to carry on round then.
When overtaking you will normally be maintaining, or increasing speed. I doubt that the cyclists would slow in that case. However, you were slowing to make the left turn. In that case, the cyclists would be riding into a closing gap until you have made your turn. If you had pulled alongside and then seen the junction, the chances are that you would momentarily have slowed before making the decision to carry on. IMHO that could be enough to cause the cyclists to slow.
A problem for some candidates on test is that they think they must follow the examiners directions. This can be a problem when, for example, they are asked to turn right on a two lane road (dual carriageway). I always emphasise to my pupils that you only make the lane change if it's safe. If not carry on in the lane your in. The examiner will re direct you, and you will not be marked down.