I agree it's unlikely you've got legal expenses cover.
Even if you did have the cover, legal expenses insurers are very wary of funding neighbour disputes as they can be long, contentious and expensive, and are rarely fully resolved to anyone's satisfaction. They would need to be sure there were good prospects for success before taking the case on. Suggest you contact the helpline you do have and get some advice on how strong your case might be, then approach a local law firm and see what it would cost to pursue. Be warned though, an ongoing legal dispute would also make your home very difficult to sell if you wanted to move - you'd have to disclose this to the buyer.