Funny I went to Coventry in 2006 for the same thing, but the consultant there was adamant that the SIJs are the only joints in the body that don't go wrong, despite extensive conversation with his secretary beforehand to make sure I didn't have a wasted journey. I was always sure it had more to do with his running 2 hours late, which was helped more by getting rid of me in 2 minutes. Still I didn't pay his request for £250 cos he didn't do anything - not even a letter to the GP. I felt like suing him for my train fare, as I wasn't allowed to drive with injections promised.
So I got it done elsewhere. But my whole body was a very big mess beforehand. My pelvis was and remains twisted, my glutes were non-existant, I had scoliosis, bad neck etc etc but all improving very slowly. I think the most important is to get the fundamentals right. So if your SIJ ligaments have stretched out again, why not repeat the injections? With a more stable foundation, the muscles work better. If the whole pelvis is twisted and back gone, then it is a big job to straighten it all out, especially in us hypermobiles. I mean there is no quick fix. I went years with no progress. Best read this forum for lots of tips about core stability, orthotics, especially the SI thread. I don't think many physios know how to treat it, as so much muscle dysfunction affects it and can pull the joints out, especially as there are no muscles specifically to hold it in place. I speak from 10 years SI slobbing around and I'm doing better physio-ing myself, with lots of sclerosant injections.
By the way, I did find the only way to find the right internal muscle was using ultrasound despite lots of angry physios shouting at me. Where is there a physio in this country with ultrasound (and doesn't insist on yanking SIJs)?
Joint group leader for South Central (Bucks, Oxon, Herts)