Thanks for your enquiry.
I'm afraid you do have quite a battle if this Company do not willingly remove your skip. You can contact the Council as the Company should be regulated with them, but unless your Council are really helpful, they are unlikely to help unless the skip is parked on a public highway, which it is not.
Likewise, the Police are unlikely to assist as they will class it as a "civil dispute".
The only real option you have is to threaten legal action if hey do not remove it. You should either write to them giving them 7 days to remove the skip or you will take legal action against them.
If this does not work, you need to get a local Solicitor to write to them on your behalf, stipulating that they will issue Court proceedings against them if the skip is not removed forthwith.
Hopefully this will do the trick!
I am sorry there is no magical solution to your problem.
If I have answered your question, I would be grateful if you could leave positive feedback.