There are regional variations, of course, but, broadly speaking, it is condsidered the height of bad manners to peer into anyone's front window as you walk past. (You have to realise that the window looking onto the street is the "front parlour", the posh bit of the house where one does one's entertaining. Day to day living is done in the kitchen, and friends and neighbours, in many communities, don't knock on your front door - they come round to the kitchen door.)
Exceptions are members of the family (including those who don't live in that house, like married daughters and sons, their spouses and off-spring, gandma, grandad, aunties and uncles etc etc
ad nauseum.) Very close friends may be allowed to do so, if they were about to call but suspect that you have "company", in which case they may peek to check whether this is the case. They may then make a decision on whther it polite or not to knock at your front door. For instance, if it is an old mutual friend, it just might be permissable to call in to add to the party, although in many communities you would, even as a close friend, wait to be invited.
When you move into such a community as an outsider (an off-comer") you find out about such niceties pretty fast, if you wish to be accepted at the end of twenty-five years!
As I say, this is a broad generalisation, (and I do not doubt that a number of people reading this will say -"'e don't know what 'e's bletherin' abaht.")
Also, this is a style of life which is tending to disappear, although slowly, because England has a large stock of such terraces, most of which are still in very good repair, and make very good, cheap first-time-buyers homes.
However the community spirit that went with this type of accomodation no longer exists, except in small pockets - the working and living conditions that engendered it have gone, thank goodness, although one mourns the loss of the emotional and practical support that it brought.
