As said above, if the needle is at "2 o'clock" then this is normal, mine runs at that and always has, i dont have a vented bonnet so have put it down to that, when driving it will drop abit but is rarely below half way after 10 mins of driving tbh. you could fit a manual switch to the fan, you just literally just splice into the loom off the fan wires and put a switch somewhere on your dash.

or fit a new thermostat and fan switch. they are known to work intermittently when they get worn.