Just a for info which is worth a try for anyone with what appears to be an unsteady internet connection.
I struggled with this issue for a few weeks before I thought to try something which I was doubtful would have any effect, but after 3 weeks of a rock steady connection, it turned out to be the fix.
Tried all the usual things with my Belkin Wireless Router, including contacting my ISP who assured me my signal was reliable and steady, (I didn't 100% believe them). Kept rebooting the router which is the first thing to try, and tried changing various settings, and then changing them back.
In the end the fix was to simply reinstall the saved configuration file I made a few years ago when I first got the router. Simple as that. The change was instant, and the signal hasn't wavered since.
I did initially try a different wireless router, but it was a s**t old model supplied by my ISP years ago. It was never any good and couldn't hold a steady connection on a good day.
With any luck, this may help someone else. You never know.