That looks pretty good to me. Don't worry too much about the Speedtest.net result not being at 140-150 mbps, sometimes the test server being used isn't always quick enough ( you can change the server and try some others out to get a better idea of the average speeds across them). You've got a good ping too.
Seeing those results means that there is nothing wrong with your actual service from BT and that the internet you are getting is what would be expected for the Fibre 100 package.
With these wried results and how consistent your other tests were at 87-89 mbps, it suggests that your wifi performance is not great. This could be down to lots of different reasons or a combination of reasons, which you may have to do some detective work into. There could be some interference somewhere, your hub location may not be ideal for where your devices are located, the wifi channel may be congested, the building materials in your house (for example internal brick walls vs. plasterboard walls), the hub itself. That is just to name a few.
It's very difficult to determine what the cause may be, as everyone's environment is unique, so it's hard to give you any specific advice for improvement.
As a first step, you could try turning off Smart Setup:
https://www.bt.com/help/broadband/what-is-smart-setup-on-the-bt-hub--how-can-i-turn-it-on-and-off-
You can also try changing your wifi channels and seeing if that helps, in the case of congestion on the channel:
https://www.bt.com/help/broadband/how-do-i-change-the-wi-fi-channel-on-my-bt-hub
When you got your earlier results (87-89 mbps), were you stood relatively close to your Hub and in line of sight or were you somewhere else in the house? Another room maybe?
