There are very few Orthodox churches in the UK but if you are moving to London you are in luck as there is a Russian Orthodox Church and details are here www.rocor.org.uk/
There are also Greek Orthodox and British Orthodox (offshott of the Coptic Orthodox Church)churches in the capital.
If these are too far away from where you are living then it is worth trying some local churches. Many Orthodox end up worshipping in Roman Catholic Churches or in C of E churches that are in the catholic tradition.
Where I am there are Romanian and Syrian orthodox churches that share space in Church of England churches, usually worshipping on Saturday rather than Sunday. There may be more that I don't know about.
If im.correct, i believe there is a russian orthodox.church in chiswick. Which is in west london, zone 2/3. They were very charitable when i was working with another church there, and their building is beautiful.