Ground rent for flat based on RPI

Hello!

So I'm looking at buying a flat and was concerned about the ground rent increases. Apparently around 2011 ground rents routinely were setup to double every 10 years. The one I'm looking at starts at 200. So every 10 years it would've looked like this..

200 400 800 1600 3200 6400

So I was worried and contacted the sales office to question them about this policy. They told me it's now based on the RPI and goes up every 10 years. They didn't give me any other specifics at this stage.

My question is. Is this a good or bad deal? I've heard this is normal but I'm worried I'll end up with a property no one can mortgage. This apparently happened with lots of buyers of the double every 20 years model.

[Property]