How can i go to the heathrow airport terminal 3 on 25th dec 2011 plz guide me i want to go on public transport?

Heathrow Express is running, as are a few buses according to http://www.tfl.gov.uk/assets/downloads/festive-leaflet.pdf

cab to victoria then coach. there are no tubes on christmas day

I would avoid that, if I was u coz theres no public transportation anyway. Book a mini cab - private... by today (don't book a taxi, it will be too expensive on the 25th, because it will be christmas that day). and if its too expensive for u, ask around in ur local area or if someone could drive u to the Airport. The parking itself would cost ur friend or relative sth. So offer money. Offer money to ur friend or relative, at the first place when u ask to drive u and explain: that its ok for u and u understand his/her financial life and that it is normal to take money and u dont really mind, but infact u'd not feel shy takin the money. also explain that ur flying and do have only limited money/budget which is for ur holiday and if ur friend would take u or relative, that it would be much cheaper for u. Let him/her know that you'd pay him/her. Or ask asian ppl in asian shops and offer them money. Make sure u'll ask him to come over and 3-4hours before u fly. And even if the person is reliable I'd leave home 4h earlier!! Christmas traffic u know...and asians do not celeb. Christmas btw. And Asians are famous for being late lol

Difficult. No public transport on Christmas Day, so you'll have to get a taxi to Victoria to get the bus to Heathrow. It'll take forever and the taxi will be really expensive.

There will be a regular bus service from Paddington Station to Heathrow on Christmas Day taking 45 minutes(substituting for the Heathrow Express train) www.heathrow express.com

There is *NO* public transport on Christmas day. And all the Taxi's that are around will charge you double fares. Good luck.