Hi Gareth, long time no forum-see - how are you!?
Re. the site. I think you're spot on: it 'does ok' but it could do better. There's loads to read - but it's almost too confusing with all those internal links. I lost track of where I was quite quickly.
I think pop-out images are only worth having if the popped-out image is a lot bigger than the thumbnail, otherwise the viewer's left wondering 'why?' ;-)
The site jumps about a few pixels here and there and there are some gaps between the sections that make it look like a badly built house
The huge list of towns (you hope to be found in Google for) looks a bit spammy as does the variety of (non-relevant) links on your links page. I'm not a Google expert by any stretch of the imagination but I don't think either of them help your search engine visibility anyway (your page titles are doing that job for you).
I searched "home security langport" and you're nowhere to be found (same for most of the other towns you've named at the bottom).
By contrast, you're top 4 for "home security yeovil" because those keywords are in most of your page titles.
Ultimately, well done for building a site - not an easy thing. I presume you've saved some money, learned some things... but the flip-side is a site that looks like your priority was saving money & personal achievement above customer experience. I'd always ask 'is that a smart choice'? I'm not sure it is, but in your trade, it might not matter.
Hope that helps!