One of our dimplex night storage heaters seems to have a sticky thermostat - this morning it's really hot - simple question but how do you get the front cover off ? There are no screws showing and I would have thought you just lift the bugger off but all my pulling etc hasn't budged it - tried googling the answer but no success - the heater is nearly 30 year old - we moved in to our house when it was new and this heater and all the others have never been a problem till now - we have no gas in our village so have to suffer these outdated heaters.