Suspected Fraudulent Planning Permission

We bought a property from a private developer. They have converted a Victorian property into two flats and sub-divided the garden into two as well. The lower ground floor flat (ours) has part of the garden which is attached to the flat on the lease. The land behind was segregated but we were told that it would be storage for their builders. After looking into it a bit more, they put in planning permission for an office building (to be built in the land behind ours) for the ground floor flat. The original plans were rejected by the council with the only condition of approval that it would be solely for the use of the ground floor flat and shall not be used as a separate dwelling. After applying with many graphics and plans that were rejected, they created some that the council were happy with. These still do not match the plans of the land at the rear, nor our garden. They were all just uploaded to make sure they got the correct decision with the pure intent of breaking the permissions afterwards.

The day after we completed, an auction sign erected for the land at the back of our garden. The auction house were advertising it as a freehold office building plot that could be turned into a two story house. This assumption was easily taken apart by our arguments, but it was eventually sold. It could potentially have a huge effect on the valuation of our property.

The developers insist that their intention was never to sell the land, but it was a last minute plan. Good timing, especially as they lied to us throughout the purchase and agreed that they were complying to planning permissions. What we can see from their advert was that they had a graphic that showed the planning of a two story building, but they also said this was created last minute and well after the planning was agreed. I have run a check on the image uploaded on their website and it shows that it was uploaded and created before the planning permissions were given, showing that they had the full intent of breaking the permissions and that they filed a misleading/fraudulent application.

Thus far, these crooked developers have got away with this. I want to know whether there is anything I can do to sue the developers or take action against them for deliberately breaking permissions and filling in an application fraudulently? There must be some way we can fight them as they will be doing this to many more people around the UK. It has cost us a lot of money in legal fees to fight the sale of the land and have lawyers look over paperwork. They seem to think it’s up to the council if I find proof (the photo and timing of its creation would suffice).

Any suggestions?