il barbi wrote:
Do you connect via dial-up, ADSL, or via a wireless [internet] (USB)
modem?

I connect via wifi since no provider offers wired connection in my area, I
have a D-Link DI-524 wireless router receiving via cable from an aerial
and
serving a domestic LAN with 2 PCs via Ethernet cable and a notebook
wirelessly

Does the behavior persist after 21:00 local time or later or before 06:00
local time? Is it worse on weekends?

I don't notice any significant variation of behaviour in a day and in a
week
anyway from sometime things are beginning to go ok, I think perhaps we got
it

Just like your mobile phone, you're dealing with two service variants right
off the bat: Signal strength and signal reliability (continuity), both of
which are weather-dependent. Then local traffic on the domestic LAN further
"splits" the signal available to all 3 computers, and connecting wirelessly
(the Notebook PC) limits signal availability, too. Chances are you do not
see these time-outs (1) when the weather is clear, (2) when you're
connecting directly to the router, and (3) when the other two computers are
not connected.

Compare to the public water supply to your home. If one person is running
water in the kitchen and another person flushes the toilet, water pressure
in the shower will decrease (and the person in the shower may get scalded by
hot water).