So,

 

I left my sex wax on the cloth/fabric passenger seat and the sun melted it into the interior of the seat lol, you can feel a hand palm sized lump when you sit on it.

I gave up trying to get this out last summer and just put a cover over it, but I really need to get it out to be able to sell the car.

 

It melts at quite low temps but other than warming up a cooking tin and putting it on the chair and then somehow sucking the now melted wax through the cloth into a vacuum cleaner I'm lost for ideas

 

Any advice?

Its a skoda yeti, as I can't edited the post

Try blotting paper and a warm iron, the paper will absorb the wax.

WD40 may help to clean any residue followed by some detergent and warm water.

Good luck.

Find a car upholsterer repair shop. It will cost you but they will be able to remove the seat, remove the cover and clean the wax off the foam section of the seat. I recently had a cloth panel from one of my seats replaced by a firm that specialises in car upholstery and it wasn't particularly expensive. You might get this done for the cost of an hours labour? Depends on the age and value of the car I suppose as to whether it's worth it. If you are near SE London I'll PM you with the firm I used.