I have a hotpoint aquarius condenser tumble dryer

I had same problem.At the bottom of the dryer is a panel that pulls down.Located behind that is a vent box,held in by 2 plastic clips.Unclip the box and pull out.Yours should be completly blocked with fabric and fibres,as mine was.All you have to do is take the top section off exsposing the vents,take it out in the garden,and get a hospipe with a gun on the end,then shoot jets of water down the vents to clear all the grim.Once you have done this ,shake off excess water and replace.Your tumble dryer should heat up now,if it doesnt you need new thermostat

sounds as if your heater or thermostat are defective.