Cenvat credit on advance paid ?

without invoice cenvat credit is not possible, if you need tax credit, then ask the vendor to provide the part by part invoice. 

Since service tax needs to be payable by the service provider on receipt of advance also, a proforma invoice mentioning the receipt of advance, charging the service tax to the extent of advance and complying with Rule 4A of Service Tax Rules, can be requested from them, on the basis of which, input credit can be taken.