If you're on the Big Couch Potato Package then you may be eligible for a free booster. But they're very poor value if you have to rent them from VM, and even if free they don't always work terribly well.
My advice is to cut your losses, forget about crummy powerline boosters, go to Argos and buy this, or Currys and buy this. Put the hub in modem mode, turn the hub off, connect your new mesh system, turn to the hub back on, configure the mesh system following the makers setup guide, and banish wireless problems forever. I use a TP-Link Deco M4 myself, and at the time it seemed a risky and expensive gamble. In hindsight it's been a fantastic buy, and I wish I'd bought it years ago.
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