If the value of your contract is greater than the SDLT threshold, then you would be liable to pay SDLT, as it applies to any transaction in land, not just freehold sales.
I work with senior execs who come to the UK for 2-3 years, with their employers renting v. expensive London properties for the duration. A recently-closed 'loophole' made it income tax efficient to pay the full amount upfront - this would usually make the transaction subject to SDLT.