i did it exactly the same but ther is no need to drain coolant you will only loose a small amount.
and you have to loosen off the plastic pannel between the enging bay and the wiper bay
nigel bown
January 2009
drain coolant. remove panel underneath windscreen wipers.disconect both hoses.unclip heater valve(got ours off e bay £22.00+vat.)fit new valve make sure in-out arrows line up as before removal.flush radiator system.add coolant top up.no more cold toes.