The Hub4 wifi is not any better and forget the Hub5. VM dont "guarantee" wifi
You can try this on a Hub3 it often helps....
Try separating the SSID's of the 2.4 and 5 GHz wifi bands by renaming them in the settings and at the same time switch off "channel optimisation/Smart wifi” “ apply and save the settings. All wifi devices will need reconnecting to the best SSID at each location. Also use a wifi scanning App to find the best wifi channels to use (just select and use channels 1,6,11 on 2.4GHz) - this often helps Hub3 users get better wifi performance - but its still no substitute for getting better kit 🙂
To address the wifi issues, VM now supply “wifi Pods” (no longer doing cheap and cheerless “boosters”). However, their Pods are only free to customers on the 1GB, Ultimate Oomph or Volt packages - is that you? If so they are worth trying - they should work for you.
If not… you will be charged £5/month. Its a simple solution and should work for you. However, I guess that's a non-starter for you.
I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.