* UAE markets retreat as local and Gulf investors sell * But Air Arabia rises on $230 mln aircraft financing deal * Saudi Arabia's petchems remain weak as oil slips again * Qatar resilient after string of positive news * Egypt's Oriental Weavers surges as market digests Q3 results By Olzhas Auyezov DUBAI, **v 19 (Reuters) - Weak oil prices and global equities kept most Gulf stock markets jittery on Wednesday, although a glut of upbeat news lifted Qatar's bourse to an eight-week high. ...