@oliverthompson79
With your new powerline devices where one acts as an access point, you'll have given yourself two setups to try, so it would be pretty bad luck not to get it all working one way or another however there are more variables to play with. The two setups are broadly:
a) Ignoring the inbuilt AP of the new adapter and just swapping like for like the new powerline devices with new ones and hoping that because they're newer/gigabit that they'll support larger frame sizes.
b) Using the access point facility in the new powerline device and in effect bypassing Sky Q's problematic tunneling for LAN traffic between non Sky Q devices.
So for b), which is the current plan, what should be possible is to in effect bypass the Sky equipment entirely for traffic between a control device and the Hue hub. The Sky Q router will still do DHCP to supply IP addresses but that will be about it. You'll need to disable any DHCP server inside the powerline adapter that acts as an access point therefore.
I'd focus on just that part first, so ensure the Hue hub is connected close (no Sky Q equpment in between but switches would be OK) to the powerline adapter in the house, and a have phone/comupter acting as the controller to switch lights on/off connected to the other powerline adapter's access point in the garden office. I'd not have any other powerline adapters in use either, just the two between the house and the garden office.
I'd recomend having the Sky Q mini box switched off when you first do all this.
This way you'll just be testing the effectiveness of the powerline connection on it's own so to speak.
If it doesn't work then there is more to the story (like another device) in the mix.
If that all works then turn on the Sky Q mini box.
If things start going wrong from that point then there are things to try and more specifics to dig into.
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If you did want to go with a) instead then the feature to search for spec wise for the powerline adapters is support for 'jumbo frames'. Note that it will not be on any spec sheet, but you may find people asking about support for these in forums that reference the particular model's you've purchased. I myself have TL-PA9020PKIT AV2000 adapters and tested their capacity for jumbo frame support by putting a computer either side of them with jumbo frames enabled on the ethernet adapters of each computer and pinged between them using the options discussed before.
However if you're going with option b) then don't get hung up if your new powerline adapters don't support jumbo frames. It would have been possible for example to have used the old ones and added a basic access point into the garden office to do a variant of option b. This AP being normal would not try to tunnel LAN traffic to the main sky Q TV box like the Sky Q mini box does.
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I do have a sneaky suspician that there may be some more to this that isn't evident from the thread, so if nessesary, drawing a diagram that has everything on it could help as perhaps there is an old swith or another set of powerline adapers or something in the house that isn't playing nice.
I also have another thought that the powerline connection from the home to the garden office might not be all that reliable and perhaps sometimes worse than an wireless connection. This would explain why sometimes things work and sometimes they don't as wireless connections have a larger permissable (as standard) frame size which is more than enough for Sky Q's tunnelling, vs wired connections which if they all kept stricly to standard won't work all with Sky Q's.
