I am not familiar with Blink products but doing a quick Google search it seems they run on 2.4"ghz WiFi.
I also did a quick search on the Sky Broadband Community and the only thread I could find with regards to Blink was that splitting the two WiFi bands on the Sky Router (NOW Hub clone) worked for the Blink.doorbell owner who posted on the Sky Community.
Maybe try splitting the 2.4ghz and 5ghz WiFi bands again on the NOW Hub 2 Router and take the 2.4ghz WiFi channel out of automatic and try a manual channel instead.
Also perhaps after doing the above try a full reset on your Blink devices.
Hopefully somebody on the forum who uses a Blink doorbell or mini camera will give some further advice.