EGLL is controlled from Swanwick control center in hampshire. They transfer to the tower when they are about 5 miles out (i'm not an ATCO so it might not be 5 miles, but they are usually pretty close!)
Multi Controllers is simple. Two Radars, same frequency and an understanding of what each other will do.
Wind is critical closer to the ground! Once you are at height its not so much of a problem but if you are low and slow it is very important!
Not sure about the frequency for approach, sorry.
With a bit of luck an ATCO will answer your questions! (and correct my answers!!)