Ah! i had one of those with my iMac. Changed it to a Lenovo wireles one and ne'er a hint of trouble from that day on.
Does how you wake it make any difference?
If you have phone and broadband with BT , most likely as you have received notice, and happy to stay with them just select the broadband speed you want with 'digital voice'I have now had notice my landline will be going digital. Something else to get used to.
This may be the key. Over time, bits of stuff can become corrupted, though often not in a big way. Turning off your computer - a proper turn off, not a re-start, will often re-set minor problems. because the system checks a lot of stuff when it reboots.Thanks again @nitram.
Instead of leaving it on sleep overnight I`m trying to shut it down completely and so far so good.