Gaing access to flat above with leak into my property

[roadie3rd]

I live in a ground floor 2 bed maisonette and we have water dripping through the light fitting in the nursery of my 8 month old kid. I own the freehold to the building and upstairs owns her property as do we (we do not rent) We noticed a slight staining of the ceiling a week ago and thought nothing of it. On monday we had water dripping out the light fitting. I tried knocking on upstairs door but no reply, so i called our local friendly builder to take a look at the situation. After the builder decided to start cutting a small hole in the plaster board to have a look what was happening he said that it was coming from somewhere in the flat above and he needed access to locate and sort the problem out. Unfortunatley no one was in. I managed to track down where upstairs worked and after 2 days of calling her work i finally got to talk to her and explained the situation and that we need to gain access to see where it was coming from. She said that she didnt think it was coming from her as she said she checked to see if anything was leaking when we mentioned it the first time a week ago. She also mention that she would be unable to get to her house till xmas day as she is working and the snow is to bad to get there (its not cos ive managed to get to work every day 50miles away, she works 5 miles away) so she is staying with a friend. I said this is very inportant we need to get into her flat and locate the problem but she said she was busy and hung up the phone.
My wife and kid have had to move out and go live with my wifes parents as the kid cannot sleep in her room as its a health issue.
We dont realy get on with her upstairs as we have had numerous problems with noise at unsociable hours (music, tv, washing machne at 1.30am if not later) My wife isnt taking this very well and to top it all of we are trying to sell the place
What can i do?

[redcrx]

call the local police station and ask for advice. They will probably try and gain access.

[The Builder]

I don't know, but possibly, the Police wouldn't be interested as it's not a "criminal" problem.
I would guess Environmental Health would be the ones to contact. I should imagine they either have power of access, or, at least could authorise the Police to act.

[DTCwordfan]

(i) local police - they will know I suspect

(ii) Citz Advice?

[ChuckFickens]

Is there not a separate mains water feed if it's a separate property?

If so can you just turn their water off?

[roadie3rd]

Ive just been to the police
they said as im the freeholder i can take her to civil court or sue her for damages as the freeholder not the owner of the flat below
but with that either way it leaves a dark cloud over the sales of my property