Is it a heater under my leather seat?!

Hello , I have the mk 3 58plate , leather seats , now… I ve noticed the other day as I was sitting right under my bum at the back
Feels like a small lump …the drivers seat has it too but the drivers seat the leather is more new the drivers seat is softer as get used more
So the other day as was waxing the seats I thought oh…what’s that? Is it the heating? Believe it or not I rang mazda Guildford and beaconsfield in
Surrey and berkshire the service department and the couldn’t tell me , the service department in Guildford said usually u shouldn’t be able to feel any lumps on the seats but I can see them r there …really they shouldn’t be there? I don’t know they told me to take the car and they can take apart the seat to check …what do you think ? Any ideas please?