Way too many variables to really comment on troubleshooting broadband connections. Though here's a site
with some of the basics to consider. Of course you have to ignore any reference to providers as they are all in the US and not in the UK.
https://www.usnews.com/360-reviews/services/internet-providers/ways-to-increase-internet-speed
A real simple way to deduce certain problems is to connect to Ethernet if you can, just to see how fast it is relative to your wireless signal. Keeping in mind that a wired signal has far fewer problems in comparison. Especially if you live in an area saturated with wireless signals with a fiber optics network as I do. Where running wireless gets tougher every year.
Another thing you can do regarding troubleshooting is to download a freeware Wifi-Analyzer program that allows you to move and adjust your wireless router and network adapters to see whether it enhances your signal in real time. Where you adjust antennas one way and your signal increases. Move it another way and it may degrade. I found this one to be helpful in terms of wireless, though I generally stick to using Ethernet almost exclusively. Much better signal and 100% consistent in comparison.
Apart from a neighbor's wireless possibly interfering with your own, it's also possible that you may have dense metal objects located between a router and a network adapter. That will certainly attenuate a wireless signal. Something to check as well using a WiFi analyzer program. Ideally you want your router, modem and network adapter to be within proximity of one another, separated by no more than one wall.
You should also be able to find this program in the Microsoft Store. I've used it in the past and liked it.
WiFi Analyzer — Matt Hafner
With basic cable it would be unreasonable to expect to do much of anything that would raise your connection to that of a fiber optics network, that likely runs ten to twenty times faster.
As for troubleshooting your modem, your ISP may have something online to test it. If not, well...it would really take a service call or for you to replace the modem if it was the source of a problem. With my ISP I can always take hardware in and have it replaced with no effort.
Unfortunately most broadband users aren't likely to have a clue as to how many things can impede their wireless connection. There's really a lot more to it than simply setting it up and having it "work".
