As long as you can assign the policy to the mortgage supplier and the term and amount are sufficient to cover the loan, it shouldn't matter at all. However, they can get extra benefit from you for having the policy with them, so they may make it a condition of the mortgage offer. It is then up to you to decide whether to walk and get another offer or go along with it.
Historically, some mortgage suppliers haven't given a toss whether you have life cover or not as they would simply reposssess the property. In the current climate I would think that they would want the life cover in place.