Short answer
Draw an extended centreline/approach line on runway 26.
Find TANET and draw a line from TANET bearing roughly 235 degrees (I say roughly because how to achieve the straight in is not is not a laid down procedure)
The two lines will intercept. You now have as good an estimate as you will ever get for a straight in to runway 26.
Bear in mind it is done by the area bods not approach, so the bearing to intercept the localiser may change if they tactically want to force the inbound ac on a different track due to traffic reasons (i.e. push it harder south initially so they can climb a Stansted DVR outbound behind it)
Yes - it is usually done in quiet times, but they may still be busy with heathrow/city inobunds etc as well as outbounds. I would not put off buying a house I really liked due to the straight in track - it is too variable.