@Rickyboy 

WiFi mesh, not just from Deco but of any brand, is to improve WiFi coverage. For that, you'll be paying with reduced WiFi speed.

Example:

Suppose, you have WiFi router at one end of your bungalow and near that router you are getting 400 Mbps WiFi speed. Using this number for the sake of an example.

When you are standing at another end of your bungalow, WiFi signal is very weak or nonexistent.

You deploy WiFi mesh, and if WiFi mesh nodes are properly placed and there is little WiFi signal interference, you will get stronger WiFi signal everywhere, but WiFi speed at that another end of your bungalow could be 200 Mbps or even 100 Mbps.

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Note I said "properly placed." What WiFi mesh marketing materials don't tell is in many cases you will need to spend time tuning WiFi mesh. That, again, applies to any brand of WiFi mesh, not just Deco. 

Unfortunately, one may see statements such as "plug WiFi mesh node anywhere and you'll get excellent coverage with superior speeds." That is stretching the truth somewhat.

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At this point, you have two options:

1. Spend time and efforts tuning Deco mesh, and I can help you with that, but I won't guarantee results. You may like the end result, you may not - but for sure you won't be getting same WiFi speed at the other side of bungalow as you are getting standing near the TP modem router.

2. You can return Deco mesh and try different brand (result will be the same or similar) or research alternatives.

  @Alexandre. Thanks for your response. 

I'll try various positions but of course power outlets may determine where they can go ultimately. 

  @Alexandre. 

Regarding my router should it be set to bridge mode if my Dec's are set as Access Points?

  @Rickyboy 

If you configured your Deco mesh to run in Access Point mode, you shouldn't be changing your ISP Router configuration. There is no need for that. Just turn off Router's WiFi, that's it.

Your ISP Router will continue to manage network (IP address allocations and such) while Deco mesh will provide WiFi coverage.