We interviewed 3 agents. Winkworths and MG came up with the same valuation, but MG had sold two flats in the block recently. Bairstow Eves quoted £20k more and wanted £300 marketing fee up front.
MG suggested we ask for £X30k in hope of getting £X25k. We got £X26.5k: well happy! It took them less than a month to find an excellent buyer.