You could always test it with something like the 1-month plan from Three:
https://www.three.co.uk/broadband/home-broadband - if it works, give notice to your current provider and if it doesn't, just cancel with Three. You could even configure the Three broadband hub to put out a second signal with your current router's SSID and password, so no need to change the settings on all the connected devices around the house.
I'm using a Three 5G home broadband hub bought on eBay (to replace a Teltonika 4G router) and a Smarty SIM, which gives me unlimited broadband for £20/month during the winter, but the package can be modified on a monthly basis, so gets reduced in spring, summer and autumn when away in the motorhome (and that has a router with a Smarty SIM that is paused during the winter and the package adjusted as appropriate during the other months of the year, giving a 10% discount on each when both SIMs are operational.).
Can't comment on the situation with 7 in the house, though. Three indicate average download speeds of 150 Mbps, but a speed check that I just did indicated speeds more than three times that.