Hi, thanks for your enquiry.
The Council will be imposing the overage provision to protect any part of the land they are selling. As the whole of the land Somerset are selling will be granted one Land Registry Title, the overage will affect the whole of the land and it won't be possible for you to change this in the future. Hence, even if you were to sell only part of the land at a later date, your Buyer will be subject to the overage provision.
As a side point, having read the overage provision, I note it will subsist for 50 years, and the Council are entitled to 50% uplift. An Overage agreement would normally last for 20-35 years and it would be reasonable for the uplift to be only 35% so the Council are being slightly unreasonable in their approach. However, as it is going to Auction, they won't be changing this, so it is really up to you to decide whether or not to bid.
Please note that if you were to sell the building(s) to a party who requires a residential Mortgage, the majority of Lenders would still agree to lend even with an overage provision. This is because even if the overage provision kicked in at a later date, the buildings/land would be valued more than they are in their current state. I hope this assists, and gives you an overview to make a decision.
If so, I would be grateful if you could rate my answer in the top right hand corner of your screen. Kind Regards Al