You can fix the WiFi range and WiFi security by purchasing your own router if you can afford it. Disable WiFi on the virgin box and turn it into a modem. I wouldn't go down the booster route, they may work but really they are not ideal.
You can get a basic WiFi for £50, and a really good WiFi for £100. No need to spend £300 on a "Gaming router".
If you are on the max package you'll typically get a booster for free, but additional ones will cost you £36/year which you can put towards far superior equipment that you can take with you to your next provider.
I am on the maxit package, but had to push for a free booster, it's helped but my outdoor cameras still can't see the wifi. I suspect I will need a proper router, they still are to deliver the v6 tv boxes, they installed temporary v5 versions so on UHD currently.