I would like to know if I need a transit visa if I transfer from Heathrow terminal 5 to three. I will only be staying there two hours as I will be flying to Geneva. I am a Philippine passport holder.
If your transit time is less than 24 hours and you are from the Philipines, you will not need a transit visa as long as you will stay in the arrival/departure lounge. This is called airside transit. If you need to go out from this lounge or need to stay more than 24 hours then you will need a visa.
In your case (from the Philippine, 2 hours connection time), UK border agency website says:
In addition to that, Heathrow airport has a nice service for transit passengers. Heathrow airport website describes how to transfer from terminal 5 to 3 without the need to pass through passport control.