Well done Badlad/Tim for taking the effort to look at this and provide some evidence rather than hearsay. Personally I am all for the presumption of free access to caves on CROW land for the following reasons;
1. The present situation just seems totally ludicrous, in that anyone has a right enshrined by law to be on that land, by the entrance and over the cave and pretty much do what they like (barring those activities specifically banned under the act) but they cannot progress down that cave beyond daylight. To me it seems inconsistent, and quibbling about whether caves are open air or not is semantics. My view is that caving is just the sort of activity that CROW was meant to encourage.
2. Digging - I note and understand the fear expressed by diggers that a heavy handed approach under CROW could sour landowner relationships. Firstly I don't see that there is any need to be heavy handed with landowners. I don't think (though happy to be corrected) that any English/Welsh access agreement has been renegotiated/reviewed with the relevant landowners specifically with regards to impacts due to CROW. Many of these access agreements make more sense when there was no access by the public to the land in question, and the caver's access conditions were the only possible mechanism to provide any access. A careful approach to at least some of these landowners may get them to suggest that the current situation seems a bit silly?
3. I also note the fear that land owners will be reluctant to grant permission to dig for a site (that if and when it goes) will have a right of access to it. The big issue as far as I am concerned here is that any new site dug (with the landowners and any required statutory body's permission) is already on land that absolutely anyone can access anyway - hence the opening of the cave would not infer any greater access to that piece land than already existed under CROW anyway.
4. Reduction in landowner liability - that has already been covered in this thread.
5. Future Access. Something that I don't think has been covered in this thread to date is that pertaining to future access. With the situation as it is at present we are completely reliant on the whims of landowners. As many of the AntiCROWs have been very quick to point out, on idiot can sour that relationship and lead to a loss of permission, whatever the access restrictions are. Equally a new landowner can have a different view on access (as has occurred in a non-caving situation in the village I live in). This has been vocally voiced by various diggers with regard to surface digging permission. However this can easily also affect access to existing caves. Across all regions in the UK there are plenty of examples of caves where access is denied by the landowner (I don't know how many of these are on CROW land, but that s a different point). For many of these caves extended negotiations with the landowners have failed to provide access, though patient work such as that a Pen Park can work (even if it takes decades). My point would be that if caving were allowed under CROW then landowners would in future find it hard to exclude cavers from a large proportion of our caves, this I think is a really big gain.
6. Finally I think that CROW may actually be of benefit to cave conservation in the UK? This may seem a little odd given some of the conservation worries expounded above, but I'll try to put my point across. Many of the access agreements in the UK are in operation for a wide variety of reasons other than conservation. A substantial number have been in operation for many years with little change over that time. With the coming of CROW, cavers will have to think carefully about how to conserve those caves now opened up - it is our responsibility as no one else is looking after the caves for us. Conservation is an easy and emotive subject to use to beat up anyone in favour of more open access. However, I would argue that true preservation of our caves would only be practical if no one ever went down them. Clearly I don't think that is a desirable position! I understand that CROW does allow for protection of special features on access land, therefore we will need to identify those caves which the caving community believes warrant special protection. My view on this is that the only really effective method of providing protection to a cave is by gating it and using warden led trips. So the quid pro-quo for CROW would be that a number of caves would be actively protected, and the reasons for providing that protection would have to be discussed and circulated to the caving community. This would provide a relatively high level of protection to the most vulnerable caves, and at the same time I believe reduce the likelihood of gate damage as there would be more caves easily accessible and people would better understand why specific sites were gated.
Sorry for the essay, but I really think this is an important debate.