Yes you're right of course they don't.
So we have the esri in one corner where they are effectively picking a number that TSB can live with and hope is reasonably plausible.
IN the the other corner we have the commendable work of IPW which unfortunately can only access asking price information and not actual sales figures. Then we have no real information on sales volumes.
Would not be hard to get real, comprehensive up to date information if there was a will to do it. How would one go about getting some change on this? The only routes i can think of right now are,
Petetition signed and handed to some form of representative
Work with your local TD
Call Joe Duffy

One call to his show has resulted in thousands of mobiles gone from prison cells.
Put pressure on banks, they would have the info i would imagine.
When i think about it. i don't think there are enough people who understand the market to make any of the above worthwhile. Too many people looking to sell on to the next level of the pyramid scheme/