£478 is serious money, but not out of line compared to what an American dealer might charge for the 90,000 mile service. I suggest you find an independent mechanic with Volvo experience. They should be able to diagnose your car's problems, do the 90,000 mile service, and change transmission oil, brake fluid, and all sorts of things for much less than £478. "Sputtery" could be something as simple as fouled spark plugs, fouled injectors, or a clogged fuel filter. As a first step, try using a can of fuel injector cleaner and see if that helps. Use a premium product like Chevron Techron (if it is sold there) or Ventil Sauber. Good luck.