If you haven't already, start a research log or journal (or both) for your project, and write as you go. Record what record sets you have searched, the search terms used, and the results (including negative searches).
To get a clearer picture of what is going on, create some timelines for Robert Edward Fowler and Norah, and for the properties themselves. I like to make a source list of all the sources I've consulted for a research problem, and use the list to note on the timeline what source the information comes from. You may want to make a separate timeline or source list, listing the documents and records you have in the order they were created. For example, the will you found has multiple dates associated with it: the date the will was written, and the probate date. Each screenshot you posted here has its own date associated with it.
My first goal would be to collect all the addresses the couple lived at in any record set I could find, and establish a date range for their residence at each address.
Next I would suggest making a timeline for the properties you want to know about. I would make note of any owners' names and occupiers' names from each record and put that information on the timeline. This will help you see patterns, find gaps in the timeline, and think of new research opportunties. Timelines can highlight whether you may have a stray record belonging to a same-name person because it won't fit the pattern and will "stick out".
Once you have clearer ideas of where your 2x great-grandparents were and when, you can use that as a guide for further searches.
British Newspapers are searchable on the British Newspaper Archive whether you have a subscription or not. The newspapers themselves can be accessed either on BNA's own site by subscription, or at Findmypast via their newspaper search. Look for notices of sales in the paper, which may not list the owners's name. Also consider looking at the entire neighborhood to get more context for your searches. Studying neighbors is a good way to explore a neighborhood and to get more practice looking at recordsets that are new to you.
For each record set you discover, learn more about the records themselves: who created them, for what purpose, any coverage issues, etc. The more you understand a record set, the better you'll be able to use the information contained in each record. GenGuide is my go-to site for online research guides for UK records.
When studying a property, I try to get as much information as I can, including looking it up on modern-day real estate sites. (Beware of street renamings and re-numberings.) Note down any census records you have which contain information about the property, such as how many rooms it has. Correlate information from all the records, the same way you would when studying a person.
One good resource for learning more about house history in the UK is the House History Hour website. The Twitter Moments page has links to the preserved tweets from the #HouseHistoryHour chat each week. There are several weeks of "Getting Started", "Back to Basics" and so on, chats about helpful books and other resources. The chat is usually Thursdays 19.00 GMT except for holidays; see the Schedule for upcoming topics.
