Do I have a fibre issue?

hello all
I moved from FTTC to FTP with BT a couple of weeks ago.
The speed option I went for was the 150mb package but with a free "speed boost" to 500/mb for the first month.
using the TBB test and a few others, the best results I have had is 400 down and 55mb up but usually it's a bit less. Sometimes it's a lots less but refeshing the wireless channels on the router usually sees a return to the results above.
I don't have any devices using ethernet so I'm wifi only.
The installation engineer said I shouldnt have any speed issues given the location and routing of external fibre equipment so does this seem acceptable for a 500m mb connection?
Speed is perfectly adequate by the way but just wondering given its essentially a 20% loss from 500mb.
What should I expect to see after the month ends and i go to 150mb?

Forget what the installer said, if you are testing your speed via wifi it will be a mixed bag of results.

In reply to a post by chrimbow:

I don't have any devices using ethernet so I'm wifi only.

That is your problem. If you have an Android phone with USB-C (or an iPhone 15) you can get Ethernet to USB-C adaptors that work.

What should I expect to see after the month ends and i go to 150mb?

Most WiFi 5 (AC) or WiFi 6 (AX) systems can easily transfer 150 Mbit/sec. They have more of a problem over 400 Mbit/sec, and at that point it is likely the problem will be the laptop or phone you are testing with.