I think it’s quite expensive as your still supplying all the tiles/sanitary ware for the bathroom. You could save a lot in that if you were able to get the bathroom totally stripped, it’s not a difficult job but can be a messy one. you might find they would give a keener price if all is sitting just ready to plumb/tile
I would also query the materials being over £500 considering your supplying everything else… grout, adhesive, plaster and valves are no where near that price
ETA - just seen your in SW england so that might be good for yous there lol