@Keithz 

The TL-WR941HP is not a model that is sold in the US so we would not be able to release any firmware for the product here.  Also in many of our router Bandwidth control was replaced with QOS.  I went to our emulator for this router on our EN or global community site and the product's QOS does allow you to set engress and ingress speeds of your connection.  https://emulator.tp-link.com/webpages-tlwr941hp_un_Router/src/index.html.  The lowest you can set you low piroity to would be 5%.  Since this is not a US product the support we can provide is limited to basic troubleshooting. Such as checking the hardware, helping check the settings and power cycling.  If you are looking for more indepth research into the software we would recommend contact our global support @ Support@tp-link.com who may be able to provide more insight into the router itself.  

Also QOS does not limit the bandwidth persay.  The priortiy levels simply gaurantee that % of speed to those particular devices.  In times where Bandwidth is available a device in a lower pirorty will or should get rather access to higher speeds.  Only when Bandwidth usage is a factor will the priority reservations be engaged.