Street ka burning smell.. Please help.

[Patch888]

Hi, my girlfriends car recently had a change of spark plugs, HT leads and coil pack at the local garage due to misfire issues and these have sorted it. However it has developed a burning smell but only when the heater is turned on and the car is at a standstill. Could It be any of the changes amused this? Or something else that's a common issue on these cars? The car runs and drives fine but the burning smell is quite a concern. Thanks.