If you set up a new lease with a landowner, you agree a lease amount per period (monthly, annually whatever), for a period of time. Within that time there is usually a clause to allow review/reassessment of the lease amount every few years. Under those circumstances there would not normally be an upfront sum, although some large lease values are subject to Stamp Duty Land Tax payment to HMRC by the purchaser.
If you buy the remainder of an existing lease from a leaseholder, you agree to purchase the remaining lease for a negotiated sum (the upfront sum you refer to). You may also have to pay SDLT again to HMRC, and you agree to pay the owner acording to terms of the original lease.
If you sell that lease on before the end of its term, you may be able to get some 'upfront' money back again, but there is no guarantee - it is not like a deposit, if that's what you mean. At the end of a lease, any money paid upfront has no worth.
This isn't my area of expertise, but in the absence of any other answer, I trust that helps.