For self-treatment (virtually free) I'd suggest Sarah Key's Back Sufferer's Bible (about £13) plus a back block (or a yoga brick which would set you back about a fiver on Amazon or PhysioSupplies). I suggest this is more likely to be a stiffness issue than a core strength issue, as it goes after a few miles - probably the result of joints warming up. A core strength issue would normally start surfacing (rather than receding) by then, because of fatigue.
Another thought: it might be neural. I tend to start suspecting neural/referred pain when people say they have no sensitivity around the place where they're experiencing the pain. Might be worth getting your back checked out, as it could be related to compression issues and a nerve getting irritated.
Jelly bean, have you got a foam roller (or is there one in your gym if you go to one)?
It's virtually impossible to stretch the ITB effectively; but with a foam roller you get a combination of massage with a bit of mechanical stretch (because you're deforming the tissue sideways even though you're not moving the origin away from the insertion) and this is often the most helpful place to start with ITB symptoms.
Other factors such as foot biomechanics, muscle balance, trigger points, pelvic function etc can also be implicated and generally corrected by a physio; but for the majority of people with reasonable biomechanics, regular use of a foam roller will keep you in good shape.
LOL - Dan, I am a physio, I specialise in sports and training injuries - and after 10 years in the Army, I got pretty practised with knees. Unsurprisingly, soldiers and knee injuries go together fairly frequently, with all the running, marching and tabbing they do
I've never heard of an "internal blister" before - does your physio mean bursitis (swelling of a fluid-filled sac called a bursa)? If so, a cortisone injection *may* help. I don't like cortisone in most situations, but it does seem to help with bursae. If you do have it though, make sure it's a guided injection (i.e. done with diagnostic ultrasound showing that the needle is in the right place).
Achilles problems can take a long time to heal, because tendons have a really slow metabolic rate and regenerate very slowly (compared for example to muscles or internal organs which have a much better blood supply and heal quickly). I'd definitely have you wearing heel raises (in both shoes, or you'll end up lop-sided) for as long as you have discomfort there, and you need to wear them all the time - no walking around barefoot.
Stretching and ultrasound - fine, no problem with that. Are you doing an eccentric loading programme as well as the stretching? That can really help to strengthen the tendon again - but it will take time and dedication, for at least 3 months of twice-daily exercise.
Um, what else? Get your whole lower body checked out, from pelvis downwards, to make sure you've got good flexibility and shock absorption going on, as this will minimise the stress on the Achilles. This means checking out your joints and muscles. And get your foot biomechanics checked out: important for Achilles problems.