help with overheating problem

hello:

Usually when I'm driving around town the water gauge rarely registers any heat at all. Until today...

I looked down to see the gauge in the center and slowly rising, I moved the selector switch to a/c to get the aux fans running. Stopped on the side and topped off the coolant reservoir. It when down slightly. Also checked the oil and found no signs of water. There are also no signs of oil in the coolant.

What should I check next? How do I know if the water pump went? I'm used to seeing a weep hole on the bottom of pumps that usually is an indication that the pump is bad. Does rover manufacture in a weep hole to their pumps? Test the thermostat? That seems to be the cheapest option. Do a compression test on all cyls, to check for head cracks?

Cheers, Jack