A visitor to any of the Merlin attractions can purchase a Merlin complimentary carer pass.
To obtain a complimentary carer pass, a Merlin Annual Pass will need to be purchased in the usual way; online or at a local attraction. The complimentary carer Pass will then be issued when you visit your home attraction (the attraction you chose to collect your passes from).
Here is the link to how to apply and its terms and conditions https://www.merlinannualpass.co.uk/information/disabled-passholders
You can also see what other attractions can do for visitors with disabilities.