Your results seem pretty decent - 191ms to London is definitely good.
Are you able to test another MC server?
The problem doesnt' seem to be the latency to the server rather that there seems to be a contention in terms of throughput usually it will spike up to 5/6Mb/s when loading areas etc however on Afrigreen atm it won't go past 1Mb/s which causes the spike in latency you can see on my OPIS output.
No need to test to another server as this problem is alleviated on Afrired and other ISP accounts.