We will arrive in Frankfurt in late May, and have 6 days before heading to Switzerland. Any advice on taking a train to London, where to stop on the way?

You want to take a train from Frankfurt to London? Is there some reason you need to do this by train? If you want to get from Frankfurt to London to Switzerland -- one would usually fly.

If you really do want to do this, the routine options are at http://www.seat61.com/Germany.htm#London to Frankfurt by train, though you then need www.bahn.de to see the precise details. You can book at the Seat 61 site though

Note that the fastest route is about eight hours by high-speed trains, changing trains at Frankfurt Hbf and stations in Paris. Seats need to be booked, and there's nothing to stop you spending as long as you like in Paris as long as you book that when buying tickets. But you can't break your journey anywhere else, or change your times, without the whole fare structure being changed and your costs escalating. Among other things, that means you must allow ample time (and then more) to get through immigration in Frankfurt and give yourself insurance against the plane's being late. Miss the Frankfurt-Paris train you're booked on, and the deal you've bought collapses.

It's almost certainly cheaper, and much safer, to rebook your flight to Frankfurt so as to allow a same air alliance transfer onto a direct flight to London. The airport deceitfully described by some airlines as Frankfurt-Hahn, BTW, is almost as far away from Frankfurt airport as London.

Incidentally, in spite of what the Seat 61 site says, I think, if timetables synchronise, it's faster to get a train direct from Frankfurt airport to Cologne, then a train to Brussels and a train to London (bahn.de should help you work this out).

Not only does this avoid changing stations (though, as in Paris, you must allow at least an extra 30 mins at Brussels for checkin and security), but there are bits of the Frankfurt-Cologne railway route that offer some of the finest views anywhere on the European railway system - which the TGV Est/Eurostar route via Paris most certainly doesn't.

Flying to Frankfurt to go to London is like flying to Los Angeles in order to go to San Francisco.

The first thing you should do is to see if you change your tickets to fly to London and add a leg for a flight to Switzerland.

I am a little uncertain of your plan...are you flying into Frankfurt and then heading immediately to London for the 6 days and then heading to Switzerland? That doesnt really make sense as alanRow says. If your destination is London, then book flights into London...the added cost of the trains, not to mention the time, is likely not worth the savings of flying into Frankfurt if that is why you have done this.

Best case would be arrange to fly into London, and out of Switzerland open jaw. You can arrange cheap flights to Switzerland from London.