It's not really GP's you need to noble, not in the first instance. It's NICE you need to get to otherwise GP's won't be able to prescribe your drug in the first place.
As for the idea itself, the Animal Rights issue is a complete red herring. If they actually thought about it the AR lot should support this as it will mean more testing on people who, as we all know, are less important than bunnies

. The phase of drug development this would help is well past the stage of animal testing.
In principle, having access to anonymous health records would indeed allow researchers (either in academia or drug companies) to have a better handle on clinical needs and where to direct future research. If doing so could reduce the amount of time it takes for a candiate treatment to get from the lab through to trials and into use then an enormous amount of money could be saved (drug research isn't cheap after all). Where that saving ends up is the big question and I severely doubt it would be in the pocket of the NHS (assuming it even survives the ConDem government). It's most likely to end up with the drug companies. Unfortunately the big drug companies are realistically currently the only entities that make serious inroads into actually bringing products to market, the only other entities that have the financial clout to do so are governments and I'm not sure you would really want the people who deal with safety and licencing also being the ones doing the development and delivery as it would be a fairly massive conflict of interest.
It's a crappy system to be sure but it's the one we've got.
All that's just in theory of course. In practice I wouldn't have the greatest deal of confidence in the governments ability to ensure anonymity of the data.