Technically my oil tank breaches the Building Regs due to its proximity to the boundary but the BCO allowed it.
Have you looked at your and their title deeds to see if the neighbours are allowed to run services or similar over your property? You can get these quite cheaply by email from the land registry web site.
https://eservices.landregistry.gov.uk/Sometimes there will be an easement in there allowing them to run pipes or services across your property. This would have been agreed with a previous owner. If there isn't then I believe you might be able to get them removed or use the fact as leverage to get a different routing.
However don't just go taking them down. You should probably take legal advice on what you need to do to get the neighbours to remove them. Bear in mind they may have no option but to run then across your property. In which case expect a legal battle.