I am writing a letter asking for a big favour*. I am looking for a phrase which could help me end the letter nicely. For example,
That would be really helpful of you and apologies for this inconvenience.
* Asking my landlord to prepare a new contract (as my copy is lost) and send it from a different country.
EDIT2: What if the landlord is a young person (35 years) and has a less formal relationship with the tenant?