BMJ has recently published an article (abstract) by Clare Dyer on the withdrawal of a 'passage in the draft handbook to the NHS constitution... ...to give researchers the right to trawl medical records for research participants without the need for patients’ consent'.
So, no digging without purpose and consent.
From the public health perspective I'd say this is a setback. For an avid researcher this trawling would offer immense possibilities of searching for demographical, geographical and other patterns of health status, disease incidence, risks etc.
The truth is, however, that it is (really, it is) difficult to make sure this kind of access to personal health information is not abused (and that details on certain MP's last weekend binge that ended in the ER don't appear on the front page of Sun. So in practice it is more secure (at least from a governmental perspective) to aviod the risk altogether and remove the above mentioned passage.