You have to say that her purse may mean more than given thought as if not intending to buy (if not sandwiches, something else under £15) but not making the purchase.
What could it have been, and the purse being left in the door creates space so to speak between the 2 events. (Just a different thought suggestion)
I think if to buy something then it would be within 10 minutes driving time if this was her lunch/errand, maybe cancel tennis at the tennis centre, and all the perp would have to do is erase the entry, all entrys, so i would be looking for a small tennis club with maybe son 30+ or owner coach within 10-15 drive minutes of disraeli road. As no one seems to know where she played it maybe suggests more than tennis.