You won't like me saying so, but you need to take responsibility for sorting this out. VM are not a company that provides good customer service, and there's nothing you or I can do to change that. Even if you've got the VM boosters, they're a clunky solution that doesn't always work well.
So first of all, you need to establish if the hub is working properly, because the next step is you spending money to sort out the wireless, and if the broadband connection isn't working, then improving wireless will be a possibly pointless improvement.
Connect to the hub by clicking on this link http://192.168.0.1/ That should pull up the log in page for the hub. But don't log in, just click on the link "Check router status" That'll bring up a window with five tabs. Open the Downstream tab. Select all the text (Ctrl-A if using a keyboard), copy it (Ctrl-C), then paste it (Ctrl-V) into a reply here. Post that, do the same for the Upstream and Network log. You'll get an error message when you post the Network log, just click on "post" a second time. Setup a BQM over at https://www.thinkbroadband.com/broadband/monitoring/quality that'll show what's going on with your VM connection. Post a link to a live, shared graph here and we'll see what's happening. Usually needs to run for 24 hours before we can draw reasonable conclusions, but the live graph will continuously update so you can do that immediately.
If all that data looks good, then it will be time to sort out the wireless, and what you will need to do is spend around £130 on a three unit mesh wifi system (or double that if you want a dog's doodah solution). Even when the boxes of shiney new mesh kit get delivered, you're not out of the woods. The construction you describe sounds really unfavourable for wireless signals, so you can try placing the mesh units round the property and see what performance you get, but you may find that for the optimum performance you still need to connect each mesh unit back to the primary mesh router with long Cat 7 ethernet cables. The cables are cheap, routing them tidily and discretely round a home can be a right pain, although if you need to do this it's worth the effort because you'll only do it once.
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