You should find if the car is running properly that when you have been out for a drive you come back and park up, it should not take long atall to rise, mine does, it gets to about in between half and 3/4 and the fan kicks in it brings it back down to around the 1/4 mark and goes off I am not running a GRS at current so cannot comment (although I did before and it was a pain) But I have already invested in a brand new header tank, thermo, I am going to get the EVO4 grs as it is slightly smaller so u dont get bonnet catch probs and at the same time will get a alloy rad I would suggest above Lee, another fan or a diff fan! and have them on the rad

P.S Tony is right the water sys should have pressure there!