Boiler last made in 1981 so no surprise that parts are obsolete.
I would guess a new boiler about £750
Fitter and mate for 5 days £750
Sundries, New Tank, Pipes, Pump, Timer, Flue kit, Control valve £750
Incidental material - making good holes in wall etc say £150
I make it around £2,400... More if you're having any rads replaced.
It's not a British Gas Quote is it?
Peccavi, May 2009