I agree with Clementine, capillary gauges are better (but fragile, too). With elactric gauges, there are chances that sender unit will not match to gauge if they are from different manufactureres, so readings will be wrong.
I forgot to say, you should check that the radiator is not blocked, better still to have it rodded as a precaution.
If you have the 850cc engine a good improvement is to fit the whole 1108cc radiator,with electric fan but it isn't too easy, you should replace the bonnet with the later one that has no struts, make a support tower for the gearshift lever and find hoses that will fit...
I have no experience of an electric fan on the small radiator, I am generally against electric fans (!) as the possibility of failure is much greater, and it cannot warn you.