Hub 2 and Deco mesh settings

[#1]

Hi - I have had plusnet 300 installed today.  Directly by the router, I was getting 300mbps but if i moved up to the furthest corner of the house (my bedroom), it was down to 1...  I have tried to set up a deco mesh system that I have used previously.  This is bringing the speed by the main unit down to 80, but then I do at least get 15 oin the furthest corner of the house.  I tried changing the hub2 to bridging mode but then i completely lost connection (maybe because the username and password on my deco was different to the username and password on the hub 2??). 

Is it something to do with PPPoE? The Deco is set up with dynamic IP and I can't work out how to change it. 

Do i even need the hub 2 or should i just plug the deco main unit into the plusnet thing on the wall?

I have tried searching on the forum for answers but all the queries seem very specific and not quite right for my situation!  Any help gratefully received!

Thanks

[#2]

The Hub 2 bridge mode is to bridge a LAN port to the VDSL port i.e only used for FTTC.

For FTTP  forget about the Hub 2, connect your Deco WAN port directly to the ONT.Configure the Deco WAN connection for PPPoE with your Plusnet credentials

Broadband username or login name	yourusername @plusdsl.net
Connection type or encapsulation	PPPoE Always On
Password	The password you use to log in to the My Account

[#3]

This is super helpful, thank you.  I will give it a go.  Sorry for being a bit dim, but I just factory reset the Decos and wire the main one into the ONT and then start the set up on the Deco app again?

Thank you!

[#4]

but I just factory reset the Decos and wire the main one into the ONT and then start the set up on the Deco app again?

@katieee1984 i've no direct experience of the Deco mesh system but that sounds about right.