Just a quick update on how my furbabies are getting on for those following the thread who may be in a similar situation. Things have settled down loads and now I only ever put Layla in the kitchen overnight or if I'm going out. They still come to blows on at times but for the majority are happy just to follow one another around the house jointly conspiring in mischief!
I was a little dubious in the beginning having never introduced a kitten to another cat before. It didn't help my fears with Marley being an indoor cat for almost 2 years resultiing in him not seeing another cat since he was 12 weeks old! All of this aside though I couldn't have hoped for a better outcome so have heart if your furbabies don't take to one another straight away. Layla and Marley are proof that relative harmony can be acheived!