It's advisable that a landlord obtains the guarantor's address (which the guarantor is obliged to provide under clause 15.6 of the OpenRent AST) and to have them referenced so the address can be verified. A UK address is required for serving legal notices. However, this address doesn't need to be in the contract itself.
Information on this site is by way of general guidance only and may not apply in your particular circumstances. You should not act or refrain from acting upon information on this site without seeking independent legal advice.