In reading up on the Virgin Media Superhub versions 1, 2 and 3 they all seem to have wifi performance issues - so yes pretty much anything would improve performance. Routers that have external antennas can help improve vertical reception by putting them at 45 degree angles as demonstrated in
this netgear forum post, I do this on all routers that have external antenna and get pretty good reception on the immediate floors above / below.
The TL-WR940N is an N450 router, but decent for the price (25 quid new), and it should support either the default router mode while your super hub is in modem bridged mode or you can simply disable the wifi on the superhub and put the TP-link into
AP (access point) mode - where it is only giving you the WIFI and not routing. So if you're happy with the router part of the super hub, this would work just as well.
I also use TP-Link as my go-to budget router / APs since they do have pretty good price / performance. I commonly use the
C1200 for AC1200 speeds and the
C7 for AC1750 speeds, however they do cost more but if you have more devices on your network it may be worth the upgrade.
Since I mentioned access points, you can also get a dedicated AP like the
UniFi UAP-AC-LITE which will give you the best, most reliable signal over typical home router units (good read
here on that subject). I am personally using their UAP-AC-LR version, which was literally the only solution to my super-congested townhome community where there are hundreds of APs listed in my android wifi-scanner app - tried several routers up to AC1900 and nothing would work reliably until I found the UAP-AC-LR, and now get 5ghz full bars in my entire home with no interruptions or disconnects.