Google does look at h tags to understand the structure of the content on the page better, Googler John Mueller confirmed this several years ago. Therefore it’s good practice to have your H1 as a main page or title of the piece then main subheadings as H2, any further sub-headings needed to divide content under these H3-H6. A lot don’t go to this depth and focus on H1 and multiple H2s achieving good results. When I have taken it further I don’t believe it has made a significant impact on rankings compared to when I haven’t. 
Hope this helps

I tend to use the Panguin Tool and look for sudden drops in traffic at update times - http://barracuda.digital/panguin-tool/ - it maps your sites google analytics against updates.

Hope this helps

As Donald says you can rewrite content for each location and give it a location specific flavor.

One thing I would also recommend when working on something like this is spend the time trying to get some user generated content such a reviews and testimonials. This will give it a more unique local feel.

If each location has similar products but not exactly the same could you slightly vary product focus and weight of content accordingly.

I don't know you setup or budget but you could even look to get different writers for different locations. You may even look to get different business owners/franchise managers to have input on the content for their site. In some situations you may even have some keen to write some content that you can proof/edit.

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I would definitely say that your site is over-optimised and that you are having issues as you have built a lot of landing pages for locations which are very similar just with postcodes and location names being the main difference.I know you have tried to write unique content and specific location information but it still feels very similar and over-optimised purely written as an aggressive way to rank in all these London locations. I would say your site could be classed as being full of doorway pages for all the locations and this is definitely something Google doesn't like and falls fowl of their guidelines thus hurting your ranking ability. You also don't appear to have physical locations in these places so they are more of a service area. As you aren't ranking at the moment I would personally cut everything back focus on ranking for your actual physical location then you may want to choose service areas and build some pages around these, but you don't want to overdo this and you definitely don't want a cookie cutter approach. Look to build pages that really are unique. You also need to look at building the main service areas you cover into your main navigation not at the bottom of your page.

Here is an article on Search Engine Land which addresses this very well and gives you lots of points to consider in order to help you get your site sorted and hopefully ranking - http://searchengineland.com/local-seo-landing-pages-2-0-222583

Have you also looked at how others have ranked for the main terms you mention above? Competition that is successful is always a good place to look

Hope this helps!

Matt

Hi

Are you using an international domain such as .com or are you using a country specific domain as this is one obvious way Google can determine your location other than in Search Console. If you are using an international domain Google looks at several factors to determine your location including IP Address, any address listings on your site, Google My Business and even links to your site.

Have a look here - https://support.google.com/webmasters/answer/62399?hl=en

Hope this helps!

Matt

Hi Mike

On the watermark question I would personally remove the watermark as I believe you will find that whether watermarks impact your ranking or not putting people of clicking and interacting with your images is a negative.

I would also do it from a quality point of view and I would draw your attention to Google's Guidelines on Image Publishing

"Similarly, some people add copyright text, watermarks, or other information to their images. This kind of information won't impact your image's performance in search results, and does help photographers claim credit for their work and deter unknown usage. However, if a feature such as watermarking reduces the user-perceived quality of your image or your image's thumbnail, users may click it less often in search results."

I imagine you have already had a look at this and I would recommend you go with your findings on this.

Here are Google's guidelines to Image Publishing - https://support.google.com/webmasters/answer/114016

I would also remove the watermark from you images in terms of wanting people to use images and then doing a reverse image search to find sites that use them. I would then request attribution if you haven't already been given it - great way to get exposure.

I would also try to simplify your folder structure as 9 levels deep is very deep and likely to make Googles crawl of your images less efficient. I don't understand the reasoning of an individual image per folder - something more like images segmented by subject or even month like default WordPress would make more sense.

Do you have an image sitemap in place? If not here is some more info from Google - https://support.google.com/webmasters/answer/178636?hl=en

Hope this helps

Matt