Slater- the red valves are probably pressure relief valves, designed to protect your system from a dangerous increase in pressure or temperature and these are letting by and causing the water to flow into the tundish. Check your pressure and make sure its not too high (3 Bar).
Could be couple of probs.
1) faulty expansion vessel
2) faulty pressure relief valve
3) system getting too hot
Give the red valve a twist til it clicks, this will open and close the valve and may fix the leak, if not get a competent plumber who is qualified to work on unvented systems.
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