Where is the key fob transponder receiver?

[Jamcal]

Our 54 plate Corolla verso has an intermittent fault with the key fob remote. It stops working after heavy rain and works again in dry weather.

I would say this is definately a moisture related issue. We had an earlier issue with water seeping under the top left corner of the windscreen and running down the inside of the A post and then dripping down behind the dash to collect in the footwell so I had assumed this was the source. I sealed it a few months ago and this whole area is all now bone dry despite the heavy rain yesterday but the remote doesn't work again so I wonder if water is getting in somewhere else.

I don't know where the remote transponder receiver is located on the car but maybe this is the place to start looking. Can anyone help.