Series 3 Temp Gauge reading high or n/w

After a week of checking was my engine actually overheating , have come to the conclusion - No . The gauge may be reading high, however after a good long run , am getting a warm bottom hose , and 170deg at the neck of the radiator. Which is what I gather is about right .
I changed the sender , no difference , checked connections to gauge , all good , voltage reg seems fine as no issues with fuel . I now am beginning to suspect the gauge , a month ago it would sit bang in the middle , no issue , then occasionally it would stay on the bottom , and needed a tap on the glass , it would rise to middle and hold, and now ....no glass tap required it goes straight up the base of the red .
Has anyone had similar with the gauge ? , just want to check and tick off a few boxes before I go hunting for a new gauge.
Cheers Steve

Well , got a multimeter , checked continuity , checked the ohm resistance against the figures in the recent diesel temp post - almost identical , believe it's definitely the gauge so took that apart ... a very delicate affair , couldn't see anything amiss inside , but then I don't really know what good or bad would look like , no dangling bits . However delicate is the key , when I reassembled it was worse . I must have touched or bend something now definitely buggered . Replacement I think is the order of the day . Lets see what I can pick up .
Cheers

https://www.minimania.com/Voltage_Stabilizer

This is v useful info

Having taken a few temp guages apart my advice is "don't". How they ever mass produced these and got any kind of consistencey is beyond me, there's not even a pivot for the needle, it just clips on a bi-metallic strip (slow needle), and if its the older magnetic type (fast needle) then never touch the 2 adusters, it will take hours to get near as bad as it was before you started. I have one where the needle would stick on the face, there's only 2 moving parts, must be an easy fix..........Not! A hour later all i wanted was to get the needle to stop anywhere on the dial.