Hello and thanks for using Just Answer.
I am Al and am happy to assist you with your enquiry.
You would need to see your neighbour's Title Deeds. 95% of properties are registered at the Land Registry and if so, you can obtain copies of the Title Deeds, called "Official Copies" from the Land Registry, for a nominal fee.
Here is the link to the website-
Once you have the Official Copies, any restrictive covenants will be mentioned in the Charges Register of the Official Copies.
I hope this assists you and answers your question.