Don't know where you are getting your tank from. the ones I buy are 61" L x 20" w x 22" h and I pay around €160. The tank holds approx 52 gallons. then you need new ballcock, new tank connectors, new pipe work to suit change in installation. Maybe new valves.
I'd put about €400 plus vat on it.
or
€200 labour. It could take the best part of the day depending on how awkward it is, although it may take a few hours. If installer feels it will take more than half a day they will charge you a days money.