ok, so thanks for the replies first of all, secondly I guess I should have said a bit more in my original post to spare you the speculation.
Now I do not live in the UK, I do live in eastern Europe, Latvia to be exact, we mostly use standard European style or maybe I can say international style (if there is one) sockets and plugs,
https://www.worldstandards.eu/electricity/plugs-and-sockets/
look at this webpage , the sockets we use here are the types C, E,F, they are mostly interchangeable , if one has the wall socket with wider diameter holes one can stick any type of the mentioned inside such a socket, and both grounded plugs or plugs without ground go inside.
back in the day we here had very simple two wire sockets and plugs, there was no ground connection whatsoever, I still don't have ground connections in my sockets as I haven't changed them, I only added such feature to those sockets that deal with things like water heater, or washing machine. I have dry wooden floors and mostly all new electrical stuff is double insulated so thee is no risk of running it ungrounded if one knows what he is doing.
Now the most likely explanation is Baluncore's and Tom.G oxidization as that is what I think myself could be the case, or simply sometimes the pressure against the pinks from the socket is maybe not enough and that too can cause a difference in resistance, given the device used has enough power the current going through that surface area is high enough and so a 1 ohm difference makes some heat.Well I've tried multiple devices in various sockets and almost in all of them one pin gets hotter than the other, I assume the obvious explanation would be that almost no wall sockets are made with such precision that they would have equal strength springs and quality brass,
I even tried my water heater kettle in my room where I have a selfmade high quality 6 socket extension which uses a 2.5mm square copper cable soldered to the brass rails that are inside the socket, still even though the pins were noticeably colder in these sockets , atleast in one of the six that I've tried one pin got hotter than the other.
So I assume the message to take away from this is that simple AC house electrical connections do matter, because even if a copper soldered brass connector that is almost new and fresh gives some heat in the pin then old and bit loose or worn out plugs and sockets and connections can get really hot if one uses higher power appliances, this might be especially true for US or other countries that use lower AC voltage as the current is nearly double there.
There have been many cases over the years where a big house fire in many cases with fatalities was said to been caused by a electrical heater, now would it be fair to assume that unless the heater was put directly under bed or other flammable material that the cause for the fire could have been such a bad connections getting hot and causing the wire insulation to combust or other nearby materials, because in many cases you here people saying "oh it was a short circuit" but I think that is misleading because with a short circuit there are either one of two cases, either the house has good protection and fuses and so the short results in an immediate electrical outage or the fuses have nails put inside them but then the short would cause a rather quick overheat of the wire insulation which would lead to a fire rather quickly , but such a fire that starts quickly would be noticed by the people in the house usually.
In fact in many cases you read that this process was going on for much longer, say a heater was switched on and people went to sleep and then sometime in the night the wire started so we could assume the process was gradual, sounds to me like a gradual heating of a bad connection.
Well that's just me ranting a bit about what I thought while doing this.
