Running hot!!

Hi,
My e reg cabrio seems to be running hot, have replaced thermostat and done an oil and water change, rad fan is coming on, but temp guage don't seen to be working. does anyone have any suggestions or hints on wiring in a new temp gauge if necessary?

i had similar prob recently as have others. is it using more petrol than usual?

when you say thermo, do you mean the rad switch?
rad switch from crazy quiffs fixed mine.  

clean air filter?