As already mentioned, you can only plug one unit into your hub but you can expand the first network by adding extra units to it. The procedure is detailed in the manual at
Here is a copy of the procedure
How to add more Powerline extenders to your existing network
You can expand your home network by adding more extenders to your existing kit.
1 Plug your additional broadband extender directly into a wall power socket.
Make sure the socket’s switched on.
2 Press the Link button on your additional broadband extender for 5 to 8 seconds.
Wait for the Power light to go back to steady green.
3 Press the Link button again, this time for 1 second.
4 Within 2 minutes, press the Link button on one of the broadband extenders already in
your home for 1 second to complete the connection to the network.
5 Wait for connection to complete. If everything’s okay, the Power and Data indicators on
the new extender will light up.
TIP: you might find it easier to plug your new broadband extender in the same
double power socket or near one of your existing ones whilst you set things up.
As previously mentioned, I have currently got 2 extenders plugged into the router and they both work - though I respect the advice that I shouldn’t. Just to clarify the current position, I’ve had a BT Broadband Extender Flex 600 paired to a Mini Hotspot Wi-fi 600 to give an Ethernet connection to a Vodafone Sure Signal box and Wi-fi in a fairly remote bedroom. This has been fine for some time.
I also more recently used another BT Extender 600 connected to its slave unit to provide broadband in the garage with an Ethernet connection to an Apple TV box. This also works fine (50+ mps) but I need Wi-fi there too. I’ve tried disconnecting the 2nd extender but the slave doesn’t appear to connect to the original extender for broadband, and therefore no signal for the Apple TV box. The only solution appears to be either a single Hotspot slave ( may not be sold singly) or a new set of Extender and 2 or more Wi-fi slaves.
I'm trying to tell you that you can, without any doubt whatsoever, add extra hotspots if you do it the correct way. I'm not in the least bit surprised that it doesn't work doing it the way you have.
It's your choice
Just to be clear - this would connect to the BT 600 slave unit in the garage via Ethernet and provide a Wi-fi signal. The slave only has one Ethernet port, so the Apple TV would have to rely on Wi-fi; it currently uses Ethernet from the slave unit.
Yes, but if the slave only has one Ethernet port and you want Ethernet and wifi, then you would be better getting another hotspot. Or if you only want wifi where you currently have a hotspot, swap the hotspot and slave extender and add the WAP where the hotspot is currently located.
The Hotspot isn’t working in the garage, hence my need for the WAP. I think it’s because the wiring circuit is different from the house, where the hotspot is ok throughout. If it worked, I wouldn’t need the WAP. Oddly, the broadband extenders do work giving 50mps from the slave via Ethernet to the Apple TV, against 60ish at the router.
Powerline converters can continue to work where the garage and house wiring are isolated and also if the garage is on its own spur off of the consumer unit but it is not recommended to operate them in that manner as they may be unreliable.
If you still want to go ahead then you will need one of these plugged into your router, note that this has no wifi capability.
You will also need two of the below, one for the house and one for the garage, these are the Wi Fi hotspots
As you probably know, you buy the converters in pairs (one of each), this is where the description of how to expand your network mentioned in message 11 comes into play. This sets the powerline password of all three devices to be the same (your WiFi password is a completely separate thing and will not be affected in the slightest) all three units will then be working on the same network password.
Note that the WiFi hotspot has two ethernet connections.
Hope that makes sense
Those are precisely what I have and they work inside the house (lounge to upstairs bedroom) but when I relocate the hotspot to the garage and plug it into a wall socket, it is recognised by my iPhone, but indicates “no internet available” (or similar). Despite earlier comments, I have a pair of BT Broadband extenders working from the same router to the garage giving a 50mps signal, but not, of course Wi-fi. The sender units are marked Broadband Extender Flex 600 for the hotspot and Broadband Extender 600 Ethernet for the other, which is identical to the slave unit in the garage. Both sender units are connected via Ethernet to the Router which is BThub5 C2Fc.