When I asked for a letter from my landlord the following things were I asked him to emphasize (aside from the tenancy agreement i submitted):
Letter from the Landlord addressed to the Entry Clearance Officer - Manila with the following details:
1. No. of bedrooms in the house and if the whole house is solely occupied by the sponsor or not
2. Rent Amount
3. From/To date of lease
4. Statement in the letter that husband/wife & children are permitted to stay in the said property...
Better submit a letter which is accurate and complete to avoid inconvenience. My family was granted a visa October last year in just 6 days after submission because I was really very keen to these tiny details.
I was communicating then to a Letting Agent in behalf of my landlord so they were able to sign the letter. Signature from the landlady is better if I were to ask.