Later this month I am flying to LHR from the US and my friend is
flying in from Saudi Arabia. Our planes are about an hour apart early
morning arriving.

We come in at terminals 2 and 3.

Questions:

Will be both go thru the same customs/immigration area?

In any event where would be a good place to meet, especially where
there is a place to sit down (the hips are not working like they use
to).

We intend to go to Russell Sq via the Piccadilly line.

Also, should we be able to text anywhere in the airport - cell phone
coverage?

Thanks in advance