Hi,
Only you know how much stuff you have and what you want/need to take back, so costs will depend on if you need a full or half size container. There's plenty of shipping agents around so once you've got bit more of a plan on what you do wish to take back, you can call up to ask about costs and the next steps etc. If you have the funds to get a full size container and fill it up with all your stuff without having to downsize etc, just do that? If you can downsize and perhaps only take more important stuff back, you can then save costs etc.
Cheers, DtM! West London & Slough UK!