A tricky one, but as a frequent traveller all I can do is offer some info and hope it comes to use.
Firstly, getting to Paris from the uk, my most frequent method of travel is by ferry(probably Dover-Calais would be closest to Paris) or Eurotunnel (Folkestone-Calais), or even Eurostar, really easy and simple (and quite fun actually) and to book, I suggest price comparison websites like www.ferrysavers.co.uk
, it's worth browsing around for the best price. Secondly, what else you could do is take Eurostar from London to Brussels, a high-speed train to Cologne, then the daily Russian sleeping-car from Cologne to Moscow, taking two nights. There os a lot of info on the Seat61 site, I find that a great reliable travel website!