France first Switzerland next or the other way around?

There is no reason you can't go from Italy to Provence then to Switzerland then to Paris then to London. You haven't said where else in France you want to visit.

If seeing the lavender harvests is important to you, then you should re-arrange your itinerary accordingly. After you finish Italy, do your Switzerland stuff and then go to London (Geneva to London is about 6 hrs by rail). Then get your France on with a return flight out of Nice. This will give you Provence in late July.

Thanks Sam, I'm trying to figure out the most cost effective itinerary plus catching the lavender before the harvest when they cut the crop

Thanks FastEddie, no unfortunately we can't change as flights are booked already, will be flying out London on the 29th of July. Were you saying that lavender can still be seen even after the harvest? I thought that's when the crop will be cut.

I think Eddie misunderstood the timing.

You want to be in France BEFORE the mid-July harvest so you will see the lavender in bloom, right? That is easy to arrange. From the endpoint of your Italy tour, head to Genoa and from there into France along the coast to Nice, or another of the towns on that beautiful coast. The up through Provence, loop around France, and back to Geneva to start your Swiss visit. End in either Geneva or Zurich and fly to London.

This will have younan France July 6-15, Switzerland 16-25, and London the rest.
The only deviation from your original plan is the flight from Switzerland to London instead of the Eurostar train from Paris. We have done that flight a couple of times and it is fun to see the Alps as you fly over, and try to recognize the places you have been (if it is clear). Zurich is better than Geneva if you want to see Alps.

Thank you Sasha, sounds like a great plan to me, thanks...

July 6 - To Nice/Cote d'Azur
July 9 - To Avignon/Provence (lavender)
July 12 - To Paris (July 14 celebrations)
July 16 - TGV to Lausanne (Geneva, Montreux)
July 19 - To Zermatt
July 21 - To Berner Oberland/Lauterbrunnen
July 24 - To Lucerne
July 26 - Fly from Zurich to London
July 29 - Depart London

Thanks djp_syd, could I pick your brains again? My brother has a place in Zurich where we would like to stay if it's possible, is there an itinerary that can have Zurich as the base to go around?

Here's the Swiss rail website for checking on trip timing. You can use Zurich as a base for visiting a large number of Swiss cities, including Lucerne (less than an hour), Bern (about an hour), Appenzell (about two hours), Lugano (just over two hours), and Lausanne (just over two hours). The St. Moritz area is probably a bit too far for day-trips.

The difficulty will come when you try to travel up into the Alps on a day-trip from Zurich. When you get involved with high-mountain railways and/or chairlifts, you need extra transit time. Also, the weather up in the mountains is really changeable, so it's important to be flexible about each day's plans and check weather conditions each morning before setting out. The online cameras may show nice, clear views when you start out from Zurich, but everything could well have changed by the time you arrive (having spent a great deal of money on mountain transportation) two or three hours later. Therefore, it's far better to be staying very close by (such as in Lauterbrunnen if you want to go to a place like Murren or Wengen).

Perhaps others can assist with suggestions about high-mountain options that might actually be viable from Zurich. I just don't know.

July 6 - To Nice/Cote d'Azur - 3 nights
July 9 - To Avignon/Provence - 3 nights
July 12 - To Paris - 4 nights (July 14 celebrations)
July 16 - TGV to Lausanne - 3 nights
July 17 - Day trip to Geneva
July 18 - Day trip to Montreux
July 19 - via Bern to Lauterbrunnen - 3 nights
July 20 - Day trip to Murren
July 21 - Day trip to Wengen/Jungfrau
July 22 - To Zurich - 4 nights
July 23 - Day trip to Rhine Falls, Schaffhausen, Stein am Rhein
July 24 - Zurich sights
July 25 - Day trip to Luzern
July 26 - Fly to London - 3 nights
July 29 - Depart London

Thanks djp_syd, thanks everyone for helping me to build the itinerary