We are starting our trip next year and really want to get a round the world ticket to save money on flights (starting and finishing in the uk). We really want to travel across europe and through russia by train and start the flights in china but i've heard if we don't take the 1st leg from uk we can't take the rest of the flights. Is this true?and are there any websites that will include europe in the round the world tickets?
Unfortunately that is true - it's not possible to get RTW tickets that start outside UK - we're leaving on our RTW in September - diong similar to you, but continuing overland so the first lflight will be from Singapore. I have spoken to several travel agencies and they all say the same thing - which is no! I have been advised that you can buy RTW tickets starting in another country - but you have to be in that country to get them (I haven't actually tried this so can't even tell you for definite if it is an option..!) We are just buying our tickets directly through airlines - and to be honest we're only flying when we absolutely have to: Singapore-Perth; Sydney-Christchurch; Auckland-L.A. (including very cheap stopovers in Tonga and Samoa) and the cost for one person is about: £1200 including all taxes etc (think it's actually less then this but can't remember exactly...!) There also are areas where you can get air passes in certain places which means you can get several flights in one sector for a farely good price - although again some of these require you having bought the original ticket from UK....
Saying all that I don't know for a fact if you can't get your first ticket on an RTW to Moscow - I know you can't with the ones I checked with however it might be worth just phoning some RTW specialists and asking the question - we wanted to overland all the way so I never went into much depth asking about that! Hope you find a decent enough price for what you want to do!
If you are doing a large portion of your trip overland, it might not make sense to get RTW tickets, as you won't actually be travelling RTW. There are Asian or Pacific Rim air passes that might suffice for large portions of sea that seem to be down 'round that area, a trans-pacific flight to North America and then you are all connected up by land again (except for a small niggly bit down in Panama), and then a trans-Atlantic flight. It might be cheaper to just to point to point flight rather than RTW, and a lot less rules as well.