Start at Peterborough because NLER train to London stops here. Peterborough to Kingslynn via Wisbech (because the name sounds intriguing); Kingslynn to Fakenham, and thence to Walsingham Grotto(s). Fakenham to Sheringham (YHA hostel) and outing to Cromar; Cromar to Great Yarmouth (always wanted to visit there); Great Yarmouth to Lowestoft (no other option) Lowestoft to Norwich; Norwich to Brandon Brandon to Ely. Ely to Peterborough by train. YHA Hostels: Hustanton, Wells-next-the-Sea, Sheringham. Potential Lodging Points/Stopovers Wisbech Kings Lynn Walsingham Sheringham Yarmouth Norwich Brandon(?) Ely. Look for camping pods/huts; glamping options. Stargazing? (maybe not in summer).