I bought an uprated kit from RPI engineering (V8 developments), complete and brand new for £115 and they even through in a t-shirt! A lot cheaper than standard with a nice action, I fitted it myself so as for labour ?? Not too bad to do, just a bit tight with the chassis.
I had mine replaced last year and think it was about £350 all in. From Offords in Offord Near St Neots, Cambs. Had some other work done to and Bill doesnt show a great Breakdown so that is an Estimate.