OK, here's the tap3 test, which is describes as the third even though I only did one before (perhaps upload and download count as separate tests).
This Last Test comprises of two tests
1. Best Effort Test: -provides background information.
Download Speed
1622 Kbps
0 Kbps 36624 Kbps
Max Achievable Speed
> Download speedachieved during the test was - 1622 Kbps
For your connection, the acceptable range of speedsis 12000-36624 Kbps .
Additional Information:
IP Profile for your line is -36624 Kbps
2. Upstream Test: -provides background information.
Upload Speed
8220 Kbps
0 Kbps 10000 Kbps
Max Achievable Speed
>Upload speed achieved during the test was - 8220 Kbps
Additional Information:
Upstream Rate IP profile on your line is - 10000 Kbps
Your service was found to be performing poorly.
Please raise a fault with your service provider, stating that the BT Performance Tester tool indicates poor service throughput performance after the third test.
Setting the MTU to 1492 didn't help either.