I am an Indian citizen and I do not qualify for DATV concession. Going for a trip to UK and Europe, I am having Multiple entry valid Visitor visa for UK. While on my way back from Paris I will be transiting in Heathrow airport. Do I need to take a airside transit visa eventhough I have a multiple entry valid UK visitor visa?
No, you don't need additional visa. From UK Border Agency:
So you can see there is no restriction for minimum period of stay and you can use your visa for a transit.