Hi. I had 2 calipers replaced on my X308 and from memory the items themselfs cost about £80+ . I never looked for an overhaul kit for the calipers but that does not mean they do not exist. 
Thanks for all your help Jerry.The link I gave you has everything if wanted but the calipers shown are by the looks of it complete and no need to buy the extras. The ebay ones are £70 inc postage. Have you tried Jaguar | Land Rover spare parts at British Parts UK ?
perhaps I am being thick here but I can't seem to figure out which one I need for left front. From the fitting position diagram I can decipher that the caliper is 'Trailing', however I don't get how that relates to which one to order? Jaguar XJ8 1997 - 2002 3.2/4.0 Front Brake Parts