@waiyme You can't use the Hub One in bridge mode, so you'll likely be restricted to using the P9 in AP mode. You can however use an Openreach modem (like I do, about £15 on eBay) instead of the Hub One. 

@richpriest 

I have an old TP Link TD W8980 which seems has bridge mode facility. I will give this a try. Thanks 

@richpriest 

I end up using Netgear D6400, currently using this setup where I enabled VLAN/Bridge https://prnt.sc/ti9z2n . Switched off Wifi. Everything is working fine, speed is around 43mb but it is only the 1st day connecting to Plusnet. Had 50+ when was with Sky . 

Checked for double NAT, I think there is none, refer here https://prnt.sc/tiax8khttps://prnt.sc/tiax8k 

Later on I found this option Device Mode on the Netgear https://prnt.sc/ti9zgk . Should I use this instead?

Thanks

I'd give the Device Mode "Modem Only" a go first, unless you specifically need the router to do DHCP, etc rather than the Decos.

@richpriest When using Device Mode to "Modem only", do I remove the VLAN/Bridge setting in the DHCP?

Thanks

@richpriest 

I end up getting Vigor 130 instead. it is supposed to be plug and play but P9 is simply not connecting to internet.

Vigor is saying DSL is connected but WAN ipv4 is disconnected (but I don't think I need to worry about this?)

troubleshoot the p9 WiFi on desktop saying dns is not responding

its really not supposed to be this complicated is it?

advise is much appreciated

@richpriest the Draytek does not require/does not has iSP login area, so I entered the ISP details in the Deco app. 
 

I have entered the correct setting in Deco App because it is working with Netgear Router in DHCP mode.