Rob,
Thanks so much for your really helpful insights. This highlights areas I need to hone my skills on.
To respond to some of your queries, I should clarify the category tag issue. WooCommerce by default inserts the slug "product" or "product-category" into the URL. and by that I mean those actual words.....so we would have had the URL as follows:
https://www.glassesonspec.co.uk/product-category/sunglasses/mens-prescription-sunglasses
So we had a completely useless element in the URL that meant nothing. So we emplyed the following plugin to remove the problem:
https://www.perfectseourl.com/
Hence our URL's now have no irrelavent elements in the structure. We took care to redirect any deleted categories.
Re. unique content, this is something we are addressing, we have started to create relevant blogs which offer help and advice to potential customers. New unique content is something we know we need to improve on so this is the focus over the next few months.
I take your point on the product descriptions, however there's only so much detail you can provide on a pair of glasses, and it's easy for it to become very repetitive as the differences between frames are not massive and don't give much material to work with creatively. We're currently working on the product page construction and making amendments which include adding more tabs with more information on each individual frame.
I take your point on the keyword stuffing issue, this is something I need to research more. Sadly Yoast does not seem to downscore my content for keyword stuffing, maybe something they need to address as it's clearly an issue.
Rank tracking, I take your point on this, we inherited the seo from someone who left us no notes on what they were focusing on so it's very much been a case of trial and error. We did find a lot of keywords being optimised were for very low traffic.
Regarding the submission of new links, we have the site linked to webmaster tools and sitemaps generated by Yoast have been submitted... should we be manually submitting these links too?
The industry does lull around this time of year, mainly due to the drop in sunglasses sales as the holiday period ends, but never to this extent. The drop off in sales was almost an overnight phenomenon which did make me wonder if it was down to some penalty or other.
Thanks again for your help!
Bob