assuming that the ground rent doesn't increase (I bet it does) you'd pay £84.5k over the 13 years. Inc the £500K that's £3850 per month. Plus I read it as you'd have to maintain The Grade 1 listed house for the duration. Then you get to give it back. At which point I assume they will sell it on another 21 year lease (it seems 21 or less years on a lease means the lease holder doesn't have the right to extend it).
assuming that the ground rent doesn't increase (I bet it does) you'd pay £84.5k over the 13 years. Inc the £500K that's £3850 per month. Plus I read it as you'd have to maintain The Grade 1 listed house for the duration. Then you get to give it back. At which point I assume they will sell it on another 21 year lease (it seems 21 or less years on a lease means the lease holder doesn't have the right to extend it).