So far no incidents with the cats whilst my neighbours cat is staying with me.
Been some close calls and a bit of hissing and growling but made sure neither is left unattended in the same room.
Tabby (That's the guest cat) has found out whwere the kitchen is and I keep having to go in and take him out as he tries to go into the rubbish or gets on the kitchen sides. My Yoshi is far more well behaved and rarely ventures into the kitchen and never on the tops or in the bin.
Most close calls have been Tabby's fault. My cat slinks into a corner or onto his favourite chair and avoids Tabby but Tabby likes to go near him on purpose I feel. When Yoshi is on the chair Tabby will walk under it. Tabby is more nonchalant and my cat Yoshi a lot wary. Tabby sometimes looks at Yoshi on purpose too.
It's not too bad as they are not actively acttacking each other and usually keep their distance. It's when I feel Tabby is being more intentional and Yoshi gets growly they are put Tabby in the other room and give my cat some personal time.
Edit: When I eventually get another cat to share my home permenantly I really want a black female cat and to call her Tenshi (Which is Angel in Japanese) It goes nicely with Yoshi. Or if the cat is a little demon I could go with Akuma (Demon)