Wedgewood oven problem

I very much doubt that both the original and replacement control valves are bad.

There are at least a couple of different setups of oven control valves. In one older setup, there are actually two control valves: the thermostatic valve, which the knob attaches to, and a safety valve for the main burner which is located between the thermostatic valve and the burner. In this setup, the pilot when first lit is a very, very tiny flame. When the thermostat is turned to a point that heat is called for, it adds gas to the pilot flame and also supplies gas to the safety valve. A thermostatic bulb at the pilot burner controls the safety valve; when it warms up sufficiently, from the larger pilot flame, the safety valve opens and the main burner lights. Once the desired temperature is reached the thermostatic valve shuts off the gas to the safety valve (and thus the main burner) and lowers the flow of gas to the pilot. The safety valve soon closes when its thermostatic bulb cools sufficiently, and the process repeats as needed. On this setup, it is not necessary to hold the oven knob in when lighting the pilot, but the little tiny flame can be a bit temperamental to get lit.

Another setup uses a thermocouple or similar to make sure the pilot stays lit, and has no separate safety valve. I think this is more common these days. For that, it's necessary to hold the control knob in on the pilot setting when lighting the pilot to have gas flow and keep it held in until the thermocouple warms up enough for it to stay lit. I think generally with this design the pilot flame does not change in size when heat is called for.

Anyhow, I suspect you problem is either operator error (not holding the knob in when lighting the pilot, for instance, or being mistaken about where the actual pilot flame should be on the burner assembly) or a dirty, clogged, or misadjusted pilot burner.