i'm getting to a point where i'm going to need to sink possibly the value of the car back in to the jag or half the value of the car depending on which route i take. so its not an easy run. but i must admit i've not had many problems, just lots of little fix its.
as for merc box specialist
http://www.auto-transmissions.co.uk/
the jag box is a merc box and these guys know there stuff. especially if its merc based. when i was down there, they had about 10 mercs in for work,