In CarbonTrail, a premises is a seperate physical building or area that is owned by your business, or where you conduct your business.
Examples of premises are:
Your head office
A workshop
A vineyard
A restaurant
A farm site
A home office (just make sure you calculate the percent you are using!)
Another way to understand if one premises is seperate to another, is whether you have a seperate electricity meter at each location.
If you have any questions still, just reach out and one of the team can help you out.