Hi Pete,
I assume that with h tags you mean H1, H2, .. tags? There is not really a need to add these to the links. Adding theme based crosslinks will probably a better strategy.
You could also consider syndicating content - I've seen quite a lot of examples where DIY stores or fertiliser companies created content, both text and video (how to paint the ceiling / how to keep your lawn in top condition / ...) that was distributed on 3rd party sites (with the same topics). Even if the links on these pages are sometimes nofollow - it still creates brand awareness/trust and probably leads/sales as well.
If I take the sample product page - I would however put some intro text at the top of the page. I guess most people who want to hire a tool like a pressure washer have a certain task in their head, but wouldn't directly know which type to choose. I would add a kind of guide at the top of the page (which type of pressure washer do I need) - you have an article about it, but the title is only about the pressure you need ("Pressure washing guide - Which psi do I need?"). Same applies to "Power cleaning techniques using a pressure washer" - people look for "how to use a pressure washer". Videos on how to use these tools are also great (it always seems so easy to use them until you try yourself...).
Apart from the keyword research already mentioned, ask the sales persons in the stores what the typical questions are that people have when they come to the shop - these questions are excellent titles for your articles.
rgds,
Dirk
Also be careful with the hidden text at the bottom (Read more about our Pressure washing services) - in 2013 Matt Cutts indicated that this was ok for SEO (http://searchengineland.com/googles-matt-cutts-on-hidden-text-using-expandable-sections-youll-be-in-good-shape-167753) - however end of 2014 John Muller indicated that it's not the best strategy (https://www.seroundtable.com/google-hidden-tab-content-seo-19489.html).