Its an unfortunately situation for you, but I believe your solicitor's advice is right. Although you own the land of the driveway, an easement has been provided to the owner of the land where the bungalow is. It is important to remember that an easement is connected to the land, not to the bungalow (that just happens to sit on the land) or to the owner of the land. Therefore there is not much to stop the holder of the legal title dividing the land into smaller plots and assigning the same easement to each of the smaller plots.
I know of a situation where a farmer wanted to develop redundant buildings as rural office units and couldn't because ownership of the land to the buildings was tied to a large house further up the lane - but he was wanting to get permission for a different use of the land. This is analogous to your solicitor's pig farm example, I think.
I also know of a situation where a jointly-owned private lane had one owner sell up and a developer put several dozen houses in, accessed off the lane. The developer paid the cost of properly tarmacing the lane surface up the point where the new houses were put in. This was a small consolidation of the existing lane owners.
Here's an idea. Have you examined the quality of the exit from the lane onto the public highway? You best bet might be to seek to demonstrate that the visibility splays are not good enough to allow a new development? Whilst there is absolutely no danger to your right of exit to the Highway at this point (existing use established), that's doesn't mean its good enough for a new development. Who owns the land to each side of the point to which the lane exits? If you do, get some pretty large trees in there sharpish. If you are friendly terms with the owner, do a deal quickly. I reckon that's your best bet the scupper the potnetial for PP. Post again if you want more on visibility splays.