I have filled out everything in an excel sheet. I have further divided my excel sheet into categories (one in each tab), like Furninture&HomeDecor, Clothes & Accessory, Electronic Items, etc. Basically, I have kept my BSF186 and BSF186a forms empty, with a statement like "My goods to follow is listed in the attached excel sheet".
Additionally, I have heard from some people that if you are returning the same day, you dont really need BSF186 since you wont be importing anything on that day itself. All your items can be listed in BSF186a (goods to follow).
Thank you,
Ajeya Gupta