Hi Brian, I had a 2005 X Type [2.5 AWD Petrol] with the same specification wheels. The X Type came with two wheel options, 16" wheels and 17" wheels, and I have not come across an 18" wheel option, so I would not be inclined to go along that route, and remain with 17" wheels. There is much opinion about the more comfortable ride, and some say the smaller wheels give a better ride. You can get the wheels refurbished and thee is a company which gives a discount to JOC Premium members. There are also several mobile wheel refurbishers and a bit of googling will throw up one in your area. The X type is a very nice looking car and personally I think, that as Jaguar has designed a car with 16" & 17" wheels, I would stick with what Jaguar thought was best. Regards, Peter.