In terms of the Duo assured rate, it is half of their standard product. For 99% of users, it probably won't make a jot of difference but if you have a forum user mentality and regularly check your connection and do regular speed checks than Uno would recommend that you go with their standard product. You are contracted to the Duo product for 18 months. They will not allow you to upgrade to their standard product part way through the contract.
The Duo product is on a backhaul of their choosing. They used to use a Zen wholesale, which appeared as ZW when you started the ordering process, but the Duo product disappeared for me for a few months and has now come back with ZW replaced by FTTC
I have considered it as it is very cost effective product, but the lack of assurance about what would happen if you did have issues and the 18 month term put me off.
Try calling them if you have any questions, they have people on the phone that really know their stuff.