G Visa? L Visa? sorry I'm confused.

Hi, My family and I are UK citizens. We have been living and working in Sanya since August 2015. Our contract expires this June and our Z type expire on July 20th. We will leave china for Thailand where my husband will be employed.
My question is this. Our lease expires on August 14th and we had planned to travel to the UK to visit our families and return to Sanya on August 4th, pack up, say our goodbyes and hand back our apartment.
Which kind of visa do you recommend and what documents would we need to provide? For instance wold a letter from our current employer suffice?
Obviously we would have no return ticket to the UK. we would however have onward travel tickets for Thailand.