In reply to Tezbully:
Jagged Globe, Icicle and ISM are all top notch. I'm sure others are too. You could hire a guide - I would recommend a British Guide. Eg; Smiler Cuthbertson, Bruce Goodlad or Martin Moran.
Another alternative could be to join a local mountaineering club whose members regularly go to the alps.
However, given that you are looking at a two year preparation there is time to gather some like minded people, learn and develop the knowledge and skills to climb Mont Blanc independently. Much more satisfying in my opinion. This can be through courses, a local club or can even be self taught ( with appropriate caution ). Excellent books and videos around, time to learn and practice the skills in the UK, perhaps learn with some mates and get some informal training from other experienced alpinists. The BMC Essential Alpine Skills DVD is a good place to start. As is Bruce Goodlad's book Alpine Mountaineering'.
Get scrambling, long hillwalking days, several days in a row will soon develop fitness. You have time to develop crampon / ice axe skills in winter conditions in Lakes, Wales, Scotland. You could do some smaller alpine peaks the year before the big one.
Personally I suggest learning the skills and knowledge so your 40th birthday challenge is all the sweeter!
...and yes, I have climbed MB by several different routes over the years and never with a guide.
Have fun with whatever you decide...