I purchased a Dimplex 3kW convector heater with Turbo fan, and returned it after a few days. Apart from the unbelievable noise generated by the cheap fan, I also discovered that the plug had begun to melt!
The replacement, a DeLonghi HCS, not only has twin Turbo fans which are virtually silent, but generates heat faster and more efficiently. It also has greater choice and control of settings, including, should you need it, a Timer.
If you're considering buying a convector heater, avoid Dimplex, and consider the infinitely better DeLonghi.
Even emailing Dimplex about the problems failed to elicit a response.