DSLreports is using multiple locations so if LINX exits from Virgin are an issue then you won't see it
Speedtest net will pick lowest latency in hope this is least congested route

Have a monitor across our Linx links into edge of virgin network and no sign of congestion, so it may not be the linx side itself but you people traverse the virgin core to reach that edge.

Perhaps traffic via LINX is not something Virgin worry about