Replaced thermostat and still no heat in my VW Golf?

This is a common complaint with mk2 Golfs, most of which were fitted with a heater matrix bypass valves to prevent the heater matrix from bursting under certain conditions.

These bypass valves can fail, cutting off supply to the heater matrix resulting in no heat.

Either replace the valves or remove them and fit a heater matrix from a mk3 Golf. These are stronger units and don't require bypass valves.