MSaxp, I think that the time mine had to really rest (the brace supported the arch of the foot; standard orthotics might do so reasonably well, less uncomfortably and without immobilising the ankle) was important, followed by the strengthening exercises for the posterior tibial and all the associated soft tissue structures. I minimised walking during those six months as well. In general, us runners are an impatient lot and often don't give an injury enough time off to really let it heal. PTT has a really poor blood supply; it's going to take time.
I hate to tell you this, but I think you need to do NO running while starting to not only strengthen the glutes but also the posterior tibial and associated foot and ankle structures. There are exercises specifically to strengthen posterior tibial - theraband exercises, and if you can do them without pain, single leg heel raises. Also lots of proprioceptive exercises (standing on one leg, then eyes closed, then on wobble board/cushion) and e.g. intrinsic foot muscle and toe strengthening exercises. I would NOT recommend a steroid injection as this is considered to increase the risk of rupture of the tendon.
I nursed mine through five 50-milers last year and it felt like it was getting better... Then I came off my bicycle and tore the tendon (partial not full tear). Result: five months in a PTT ankle brace (Aircast), six months of no running. Really stiff ankle once I was out the brace and I've had to restart running very carefully (taken three months to work up to running eight miles or so) because MRI indicated degeneration as well as the tear. I can now do 30 reps on the theraband exercises and 2 x 25 single-leg heel raises, and my balance on the bad leg is improving.
This is a nice introduction to ultras. Get there early to park your car where you pass it on each lap; that way you can grab food and water without adding extra distance and without going down to the big car park and back up again.
There IS water available but it can run quite slowly - it's faster to refill bottles/water bladder if you have your own in the car boot. Try to ensure your car boot is well organised so you don't lose time looking for things you've mislaid...
There's no aid station elsewhere, just at the end of each loop (so at 5, 20, 35 miles). You need to carry what you'll want in between; I didn't find that a problem. Last year it was fine weather and I ended up not bothering to carry most of my usual emergency gear - there are lots of other people around (walkers, cyclists etc.) so even if you injured yourself badly and couldn't walk, someone would be around to go get help.
The ascent in each lap is noticable, but minor compared to e.g. SDW50, NDW40, Lakeland 50 (UTLD).
I blogged about this last year - see http://runningape.wordpress.com/2013/09/24/lastly-ladybower/
Rachel: as you're coming to realise, the convalescent period can be rather longer than the initial repair period. I tore a tendon (posterior tibial) end of September 2013 in a cycling accident, was in an ankle brace until the middle of March. It's taken until now to get most of my ankle flexibility back. I also watched all my left leg muscles - calf in particular - wither and go flabby, which was pretty demoralising. I used the down time as time to work on core strength (lots of Pilates) and glutes and did some swimming (once the cracked ribs from the same accident healed enough that I could breathe reasonably). So: six months disuse, three months plus to regain flexibility. Six weeks disuse... shouldn't be QUITE so long, if you're lucky, but the soft tissues may have taken quite a battering from both injury and surgery and ligaments and tendons have poor blood supply so are slow to heal.
Most people don't do the exercises they're prescribed, or don't do them as often as they're supposed to. If you DO, it can make a real difference. Good luck!