I always used to shop around every year. I found myself being hit with large hikes year on year and having to swap insurer to get a better a deal. Back then I was using more mainstream insurers. Adrian Flux were terrible for it. I bounced between them and whichever "big name" insurer came up with the best quote, taking a couple of weeks of effort to achieve savings of almost £200.
I've been with A-Plan for 3 years now. They don't seem to hike my prices every year and include things other insurers won't. Each year I get my renewal, go to the comparison sites and find the recognised companies are about the same, if not a little higher. There's always some company I've never heard of before offering a much lower price but I don't trust them. In my mind, if they're such an outlier then something can't be right. Either the price is inaccurate to make me call them at which point the price goes through the roof or when I come to make a claim it'll be a nightmare/impossible/work out badly etc.
So, I stay with A-Plan as the price compares well to other companies I recognise and they cover my offroading, don't charge extra for modifications (including the LPG kit) and let me swap the car out for free if I need to take it off the road for repairs and drive something else in the meantime.