I've used the sleeper Paris-St Gervais in summer, and would be disappointed if it no longer runs (the information on Seat 61 is not promising in that respect, but gives alternatives); is it possible that the timetable has not yet been published? One thing to bear in mind with rail travel is that you can only book about 2 months in advance, and you then have to be pretty quick to get the best prices - I was lucky and used to work across the road from the Eurostar Waterloo terminus, so could pop in before work on the day my tickets were released.
As an alternative to changing in Paris, there may be the option to change in Lille, which would just involve changing platforms, rather than crossing town - my family have used that one travelling London-Grenoble - but I don't know what trains pass through Lille.
Seat 61 suggests 90 days in advance for some fares. I did a sample route the other day just under 90 days and found fares of about 70 pounds each way. Trying again last night couldn't find anything less than 200. None of this has much bearing on how much it might cost in September tho' of course. I'll keep playing around with all the routes suggested here.
I was browsing the Cicerone Valais guide only the other day. Looks lovely and much less developed. This trip, if it happens, is a first and possibly only visit to the Alps for my friend and I so we feel we ought to see some of the wonders of the Chamonix Valley first. If we do get another chance to go then we might branch out a bit.
