Ajay: We have spoken about the Kensington Hilton many times before. In summary it is an OK hotel. The service is by no means top-notch, the rooms are by no means top-notch and the whole place is a bit shabby and dated.
In short it is a tierd hotel, which is certainly the worst Hilton International in London - although I would guess you would know that given the price?
Popping to Paris from London for the day is no problem. Your options are essentially the Eurostar which leaves from Waterloo station.
http://www.eurostar.com
Or flights from Heathrow, Gatwick or City airoprts. Flights from all airports take just under an hour and arrive at either CDG or ORY. The main operaters are BA,AF,BD,UK,CB.
To give you some idea of frequency from LHR there is a:
0640,0650,0705,0730,0815,0820,0830,0845....
However, day return tickets can be expensive £250 ($400) upwards for Economy is normal for the major carriers, as you are potentially eating into the business market. So it pays to advance purchase.
Nick