ugh, how much does that suck? brutal. i popped my hamstring last yr but probably not as bad as i hear achilles can be. i've had the odd sore achilles and asked my doc one time when i saw him. his take? it's gonna happen to a lot of guys as they age and there is little to prevent it from happening. and then he said if one goes, the other will probably go too at some point if you remain active. i hate that kinda shit!!
While a GP may think this, a body worker may know ways to avoid or prevent damage. GP's knowledge base often doesn't include some of the finer points of musculature and connective tissue function, or prevention of injury.
I've used Hellerwork, Rolfing, RMT's, exercise rehabilitation and Physios in recovering from and preventing injuries, both soft tissue and bone. My Dr. was helpful in providing pain meds (careful!) and notes for work etc. but I would highly recommend seeing someone similar very soon after your recovery. You may not be ready to begin work immediately, but a consult and finding someone you like to work with will be useful right away. RMT's and Physio are often covered, and some of them are also trained in some of the therapies that are not so they can work those in as well.
Disclaimers: I'm a scientific, proof- based kinda guy, and have found that there is a lot that's not covered by health care plans that is good, helpful, scientific therapy. Also my mother was a Hellerworker so I assume I have some bias, but I've delved into the science behind it, and seen and felt the results enough to think that's is a legitimate therapy.
Edit: Be super careful re-introducing activity. I don't know about achilles specifically, but I snapped a ligament in my thumb ("Skiiers Thumb casing a drop on A-Line in 2001) and was told that if I re-injured it they wouldn't be able to put it back together again. Mountain biking is unfortunately a very unpredictable activity re: the strains it puts on your body.
Soft tissue injuries suck, good luck, and try and stay patient!