Not interested in a debate about the use of core stability
Maybe not but you still seem to enter into a debate for it in your previous para.

There are a LOT of approaches used in physio that are not well evidence based but this does not mean they have no role in our treatment.
This argument justifying the avoidance of EBP approaches has been given for a long time. Sure there are huge gaps in what we know works but that doesn't mean we don't start with working with what is there. There are now getting onto 2.000 trials in neurological physiotherapy. Do you really think it is appropriate attitude in 2010? I don't think it is.

For example acupuncture which is now part of the NICE guidelines for low back pain.
The NICE Guideline Early management of persistent non-specific low back pain includes acupuncture as part of a package. This is based on sound if not conclusive evidence that acupuncture as part of an approach is effective in persistent LBP, but not acute LBP. This is well reviewed in a Cochrane reivew: Furlan AD, van Tulder MW, CherkinD, Tsukayama H, Lao L, Koes BW, Berman BM. Acupuncture and dry-needling for low back pain. Cochrane Database of Systematic Reviews 2005, Issue 1.

There is far too much useless research out there.
That may be but there is also some high quality evidence out there and a much larger amount of research that is of ADEQUATE quality that can be applied to give us some certainty about what may work best. Furthermore the quality of evidence has increased considerably in the last few years. Isn't it your job to locate that which is useful rather than going for a treatment that may have no plausibility and now evidence for your patient group you are dealing with?

If any physio claims they only use treatment that has masses of evidence to support it they are lying, it's about using our tool box of skills and treatment techniques and applying them appropriately to each individual patient using our clinical reasoning skills and the patient's own goals.
This isn't an all-or-nothing thing. If there is a tool in your tool box where there is not only an absence of evidence but also evidence of absence would you still use it? I wouldn't. If there is an absence of evidence but there isn't much in the way of evidence for an alternative treatment then I would fall back on what is available. Studies of plausibility would be a good start. Evidence-based practice is not about ignoring clinical expertise or patient preferences. EBP does not preclude clinical reasoning. However it is about making the best use of what is available. And one of the unpleasantries about clinical practice is that we tend to fool ourselves into thinking we are more effective than we really are. That is one of the key reasons we are supposed to be behaving as an applied science. So we don't keep repeating the mistakes of earlier generations. And don’t start developing unfounded new treatments based on some latest fad or some unrelated area of practice.