Hello I am a lawyer with over 15 years experience. I will try to help you with this.
Dos water flow through the ditch? Do you still have the conveyancing letters and documents from when you purchased the house?
Have a look at those documents (especially the report on property and the title plan) and see what they say about the ditch. In the absence of anything specific then Section 26 of the Law of Property Act 1925 provides that "a conveyance of land shall be deemed to include and shall by virtue of this Act operate to convey with the land all buildings, hedges, ditches, fences, ways, waters, watercourses, liberties, easements, rights and advantages whatsoever appertaining or reputed to appertain to the land or any part thereof".
It might be best to assume that this is a watercourse. If you want to change a water course you will need to get permission from the local authority, usually the district council.
Have you spoken to your neighbours about this? What did they do?
You should try to dig out your report on property and your title plan from the land registry in order to work out the position properly.
If you do not get n instant reply from me this is not because I am ignoring you but because I am fitting this question around my other commitments. I will reply as son as I can.
Thanks, XXXXX XXXXX precedent already been set as most of the other neighbours have filled the ditch as it passes behind thier garden, so could I just get on and get it filled ?
I wouldn't call it a precedent exactly but the lack of action from anyone as a result is clearly a good sign. In order to work out the legal position you need to gte those documents they will either make it clear or provide useful clues.