Hotpoint tdl52 no heat, element changed, but still will not heat

Have you checked the motor? Plenty of lint and dust gets indie it. If you can remove if and use compressed air to blow it out. Also don't overlook the fact all the spade connectors will also collect lots of lint and dust which is quite flammable. Also check the tensioner and guide wheel they get pretty dirty and when they heat up the lint can start buring.

Suspect a broken/burned off wire to the heater element, or 'open circuit' of the heater element, or thermostat fault

Check if the heating element is touching the heater box somewhere
and grounding it .

Could well be the heater, or possibly the motor.
you need to remove the back panel, and see if you can actually see if anything is obviousy wrong, try disconnecting the suppy to the heater if you can access the connections.

This sounds more like the heating element, or a thermostat.

First of all keep this in mind.
You will need to locate the wires that got hot. If you can't or if your not sure, I suggest that you call a service company. If they ok the unit and it catches on fire after wards, their insurances will cover you unit and or home if god forbid it burns. This is to be on the safe side.
Now, this is where I would look. Your element should be on it's on circuit. There should be a disconnect within reach of the air handler. Some are fused and some are not. The wires that got hot enough for you to smell them should show signs of being hot like the plastic will be melted around the wire. You said that the heater was running. Was this the first time you have used it this year? If so, are you sure it was not the dust burning off the elements? They will smell like something burning when you first turn them on each year. Although if your sure you smelled wires getting hot, please continue looking for just that. Keep in mind that the elements have 220 volts coming to them. It comes into the unit and go to a switch or relay. From there the power goes to the elements and then to a neutral. These are the wires you will need to pay the most attention to. Good luck.

heating element has blown. did you hear a loud pop at one time or a burning smell? If so this is the problem. You can find instruction and order the part you need on ebay to change the element. It is easier than you think.

Did you check the fuse in your unit ?

Check the fuse whether it is burned.

no the element, but the thermostat that turns it on, you see the thermostat works like a light switch on the wall for the house lights, it's what turns it on and off.

i am a retired engineer of 20 years, and its about a year since i worked on combination washer/dryers but if the heater elements fine and power comes from timer there must be cut out somewhere around where it should warm up, look all round the machine one may be hidden or hard to spot there maybe about 3 one of them one of them could be a trigger device (you can press a button to reset it) that style is a very small cube about the size of a sugar lump with2 spades on it, others look like a small flat oval or round shape the size of a five pence piece with 2 spade wires on them, remove the plug from wall and remove these spades and check the contacts for continuity, you need not remove from machine to do so, no circuit + no heat, replacement item not expensive, thats where to start based on the information given, check the sensors you mention again, it sounds like your so close, good luck and work safe