The tester at https://www.thinkbroadband.com/speedtest is useful as the two tests and any difference can tell people something. Speedofme can look a little odd as the initial tests are it trying to determine the file size to use for later testing

e.g. if the tbbx1 is a lot slower at peak times compared to the 1am to 8am period then congestion is most likely.

There is the urban myth that full fibre has no slow downs and while true for the connection speed, the shared nature of the bandwidth at some point in the network means things can slow down.

The local segment of fibre has 2.5 Gbps of capacity shared between something like 32 to 64 lines, so congestion there is pretty unlikely more likely this is at the exchange where data is handed over from Openreach to the BT Wholesale network which BT Consumer use.

Nah, a bad Splice would cause intermittent loss of service.

In reply to a post by Zarjaz:

Nah, a bad Splice would cause intermittent loss of service.

Wasn't too sure, its been +25 odd years since I have played with fibre, so maybe things have changed.

I know back then we saw data errors when we started to increase the speed when using a badly joint fibre.
But back then all we had was a very very fine grit sandpaper, and Eye Piece and some washing up liquid lol.

The reason that I thought it was a bad joint was where Pings / Tracing etc are not high speed as like downloading etc.

But ok, fair enough.

Paul

The only last thing I can think of is the grey box on the wall where the connectorised fibre comes from is a bit wobbly. Anyone know what�s inside? Does the cable come in as-is or is there a socket inside it that the optical cable plugs into?

It could be that that connection is dirty/loose.

In reply to a post by Brookzy:

The only last thing I can think of is the grey box on the wall where the connectorised fibre comes from is a bit wobbly. Anyone know what�s inside? Does the cable come in as-is or is there a socket inside it that the optical cable plugs into?

It could be that that connection is dirty/loose.

Does it look like one of >> these << ?

If so then its your CSP (Customer Splice Point) Box.

Paul

It could be that that connection is dirty/loose.

No it is most definitely not that.

BT don't throttle either. It's congestion.

Openreach FTTP is GPON, shared between upto 32 lines.
Someone else can do the maths, but if all your neighbours are Fibre only premises then it's congestion you will have to get used to and live with.
Changing ISP also won't help.

Connectorised don't got no CSP Paul.

Since I�m rarely getting more than 150 Mbps I am considering asking to downgrade to Infinity 3, but if I do that will my congested speeds suffer further? (E.g. if I�m getting 100 Mbps during congestion on a 300 Mbps profile, would that reduce to say 50 Mbps under a 152 Mbps profile?)

Re the grey box - it is connectorised but the grey box does look like the one linked above, albeit with only one cable coming out of it and indoors.

In reply to a post by Zarjaz:

Connectorised don't got no CSP Paul.

I know, but where the OP spoke about a grey box I was thinking maybe it wasn't using Connectorised.

Paul

In reply to a post by Brookzy:

Re the grey box - it is connectorised but the grey box does look like the one linked above, albeit with only one cable coming out of it and indoors.

Any chance in a photo of it?

Paul