After our cycle ride to Weymouth and the soaking we had on day 3 my old Memory Map 3500 packed up, in that it would no longer charge. When I came home I bought a new battery for it, but no luck, it still wouldn't charge.
It was a quite few years old and although it wasn't a "sat nav" by today's standards it suited me as it used OS maps, had a large screen, used gpx files, and was compatible with the OS maps on the PC. In all fairness to it it got us through many cycle tours.
The downside of it was that it was slow and the battery only lasted about 4 hours so on a days ride so you always needed a back up battery pack.
Memory Map no longer sell them, and finding someone to repair it would have been difficult and so I looked into alternatives.
The OS shop sells cycling GPS's complete with 1:50000 maps installed, but after looking around I finally settled on the Garmin Edge Explore as it's a basic navigation device and a cycle computer. It uses Garmin maps but as I have the OS maps on my phone I was happy with this and you can add OS maps if you wish.
It took me a while to get used to it but it has many advantages over the Adventurer 3500, the battery life is well up to a days riding and its waterproof.
I can plot routes on the PC and transfer them as tracks to the Garmin and also vice versa. I do prefer OS maps to navigate by, but as I said they are on my phone if I need them.