can you clarify how to calculate some allowable expenses for tax purposes

Tax Planning and Financial

Hi, there, I am struggling in finding the right way to put my business expenses in the right tax years. I could not find any information on the way to calculate the following:
I will give you a few examples:
these are utility bills that the landlord pays for the rental property (Leasehold)-
1. Service charge-
Date of invoice- 30.06.08
for period- 1 Apr 2007-31 Mar 08 -paid on 10 Jul 08
In which accounting year should that go and how to divide the total into monthly payments for the P & L accounting sheet which is on monthly basis for Apr 2007- to Mar 2008 or 2008- 2009???

2. Home and content insurance-
Date of invoice- 16 Jul 08-
for period 1 Sept 08 to 31 Aug 09
for total of £165.60
to be paid in 12 DD(Direct debit) payments of £13.80 starting 1 Sept 08 till 31 Aug 09- Showld I just put each DD payment in the relevant months( i. e. when paid) or do I need to make any adjustments for different accounting years- 1 Sept 08- 31 Mar 09 and then 1 Apr 09- till 31 Aug 09.???
3. Plumbing insurance- Date of invoice- 1 Dec 08- for £54.95 a year
to be paid in 4 DD payments- 1 Dec 08= £13.76, 2 Mar 09- £13.73, 2 Jun 09 -13.73 and 2 Sept 09- 13.73.
How should I calculate the amounts I need to put in each month of the 2008- 2009 year???
ANY TAX HELP on the above would be appreciated.
I also like to ask about the mobile phone bills of the landlord-
when claiming part of the calls as business calls, related to letting the property- should the calls be highlighted on the actual bill and counted precisely or is it possible to make an estimate of let's say- 40- or 50%- how does one decide what is reasonable???
Thank you so much in advance.