IMHO, manufacturers must not offer to derestrict their bikes in the first place, however tight the attached conditions are.
All fair points d8veh, I appreciate what you are saying.I have a lot of sympathy for you, because you're disappointed that you didn't get what you hoped for. Unfortunately, you hopes were probably a bit unrealistic. Basically, you're using the bike for something it's not suitable for.
Cyclotricity is not a big company. Their profit margins are very tight, at the prices they charge. You need to think about whether you're being fair to them. I can imagine that they cringe every time you call, knowing that your case is just a continuing profit drain that they can't get out of. Put yourself in their position to understand why they might be trying to avoid you. I'm not saying that they should do that. It's just that both sides are now probably in an unresolvable situation.
I think a fair outcome would be that they fix your battery, then you sell the bike on Ebay or wherever and put it all down to experience. Then you should buy a bike suitable for the journeys that you do, but I guarantee that it won't cost less than the Cyclotricity and it'll end up costing you more per mile in the long term. You can't continue with the Cyclotricity because it's not suitable.
If you claim your rights, you'll probably win. It's a question of concience whether you think it's fair.
Problem is, where I live now, there isnt rally another way to go without going down the hard shoulder of the motorway, or adding another 6 or 7 miles to the journey to get off the towpaths/tracks. At least the route isn't wet and muddy now, that will help.It'll probably be OK if you only use it on the road.