Is it a very Clean sound like a Hone (ie. not like a drill or a squirrel) and most importantly "always always always" exactly the same sound, and not a Hoooo but a HewwWWWwne (it's keeping me awake), and it's random
You probably have already checked them out, but Virgin Media are often an option. Your ISP won't suggest that, as they can't provide services over them, only Virgin Media themselves can.
Support can be a bit terrible though, but mind you which residential ISP doesn't?