Hi Geoff, I would certainly suggest having them professionally refurbished, if you are not confident to do them yourself. I had the same issue a month ago in my XK8. I was in two minds whether to replace the leather or have them refurbished. I had seen a company local to me that specialised in refurbishing leather car seats, so I took it to them about a year ago. I wished I hadn't! I had to take the car back twice as cracking reoccurred after only a few days. The guy there said it was cracking because I was sitting on the seat!!!!
Then I was talking with a local JEC Club Member who has a detailing business who also refurbishes leather car seats and he showed me pictures of some he had undertaken in the past. They look like new! So I took the plunge and had then done again, this time by someone who knew what he was doing. I haven't regretted it, he made a first class job of it. What I would say though, is if you go this route or you do it yourself, may I suggest you get some CarPro C.Quartz leather protector or something similar. This is ensure your leather stays stain/mark free for a year or two, depending on how much you use your car. So the morale of the story is find a company that is in your area and obtain recommendations. Ask to see pictures of works already undertaken to satisfy yourself that a good job will be done.