It is taking much longer to cook meats than normal despite
gas mark being retained as normal

What would cause this?

J Kane, December 2005

Most likely the oven thermostat is faulty. Remove panels to view the burner. Light the oven and allow the oven to reach high temperature. Then operate the control knob from high to low and the burner should respond throughout the range of settings. If not, the thermostat is faulty.

Liam Walsh, December 2005