Import of services

Hi this is Praveen,

Kindly help me in the following areas of Import of services,

1.Can Importer of services pay Service tax on Import of services and service tax provided by him to service recipient by single challan.

2.While calculating the service tax on imports Which date(i.e..date of invoice or date completion of service) he has to consider for applying the exchange rate.

3.And the above date will differ if he deals with any related parties.