If planning permission for retail had been refused and Dreamland's owner decided to leave it closed and derelict as an eyesore, then for the benefit of Margate the council could justifiably compulsory purchase the site. Especially if (as we know) operators are queuing up to buy the park.
This would, however, be an absolute last resort.
Remember this: were it not for planners Dreamland would now be a supermarket and there would be no Scenic Railway. It is only the fact that Thanet Council has so far said "no" to retail that Dreamland has any hope of survival. Planning is the key to saving Dreamland! What a great British planning system we have
Nick