How do I defer my place at uni for this coming year?Watch
You need to phone them tomorrow (Tues) and work through your options. At this stage they are under no obligation to defer your place until 2018. So they may ask you to reapply through UCAS next year. Also you may end up having to pay for either your first term of halls or the whole year depending on your accomodation contract, so be prepared for that too.
The only thing that can sort this is direct and urgent communication with the admissions staff, so get onto it ASAP!