Name
Job Title
Organisation
Dear [Name incl, title]
I refer to my earlier letter to [Name of organisation] of which I enclose a copy.
To date I have * not received a reply/received only an acknowledgement/not had an acceptable answer to my question.
Whilst I appreciate that [Name of person to whom the first letter was addressed] may be busy with other matters I feel the timescale I have made allowances for in my first letter was reasonable and sufficient, and believe that an answer could have been provided.
I therefore request that you raise this matter with [Name of person to whom the first letter was addressed] at the earliest opportunity.
If I do not hear from either [Name of person to whom the first letter was addressed] or yourself by[state what you think is a reasonable timescale] the I regret that [the consequences - i.e what action you intend to pursue next].
Yours sincerely