Really?
Indeed!
A slightly different analysis perhaps..

!
(Ignoring the phone issue, for which there is no excuse, but even without the phone issue the OP is IMO on shaky ground!)
OP enters roundabout in
left hand lane intending to make for the
third exit!. (Admittedly the lane markings suggest that this is "acceptable" but it is certainly unusual, and even if was a roundabout I was familiar with I would NOT choose to use that lane for a third exit entry! I would also not expect other road users entering the roundabout from other entry points to expect me to do so, so if I
did use that lane (
Despite the lane markings!) I would only do so using a degree of caution in the expectation that others might find my manoeuvres confusing!)
Initially OP is blocked by vehicle in "L2" on roundabout who is actually exiting at next exit. (Who is also "Masking" OP from approaching van drivers sight line)
Once above exiting vehicle is out of OP's way (15 seconds into the video) OP
accelerates sharply!
This is
also about the point at which I would expect the Van driver to make his "Go/No-Go" decision.! (At that point it would not appear to him that there is any approaching traffic for him to concern himself with)
Look
closely at the clip at 15 seconds. the Van is about two vehicle lengths from the give way line (No more than three) the OP is some
considerable distance back from that in a lane that has just been crossed by another driver taking the previous exit (One can see this on the video, but of course without speed data we cannot actually see
just how much speed has been gained over a pretty short time. 10-15 MPH is not however an unreasonable estimate!)
Had OP continued around roundabout in a steady and predictable manner there would have been no problem. It is the sudden and unexpected acceleration by the OP that made this an issue rather than the use of a phone!
I bloody hate people who regard roundabouts as some sort of racetrack whereby they consider it acceptable to use their sense of "Priority/Right of Way" entitlement to wilfully "Close the door" on joining traffic!