It is different for everyone. When my children were young we lived hundreds of miles from my DM and about 75 miles from my MIL and FIL so visits were less frequent than they would have been had we all lived close together. MIL sometimes complained she hadn't seen us for x time and I had to remind her she'd seen us however many times since my last visit too my own DM. Your DD needs to decide what works for her. Your DGD won't love you less by not seeing you every day and they do say absence makes the heart grow fonder.
My own adult children live a long distance from me and I suspect if and when grandchildren come along I won't see them as much as I would like, but I intend to make the most of the times we have together just as I do now.
To think that London, or anywhere else for that matter, does not belong to any one demographic