Switzerland and Paris tour query

I would apply for a visa for two entries. In the application form, Box 24 (as stated by Annoyed) offers this possibility. For the arrival date I would put the day you enter Switzerland, and for departure date the day you leave France (boxes 29 and 30), so that the visa is valid for both of your journeys.

You only have on field for the hotel, but it's labelled as "name of hotel(s)" (Box 31) so it is perfectly fine to write several adresses there.

All the documentes you need to provide as an evidence are listed here.

Clearly, you need a visa for two entries (which is not the same as a multiple-entry visa). You can specify that in box 24 but the form is not very well designed for this situation. I don't know exactly how you should proceed but the best I can think of is to provide all the documents for both trips and add a letter explaining why you applied for two entries instead of one. Official instructions don't particularly encourage it but nothing prevents you from doing that and I know some people who have had success explaining the particulars of their situation this way.

If that doesn't work and the Swiss consulates issues you a single entry visa, you can still apply for another visa once you're back in the UK. Two weeks is short but doable, especially if you have all the documentation from the first application at hand. Alternatively, if the first visa is set to expire before the date you intend to leave for Paris, you can also apply for the second visa from the French consulate in advance. As long as there is no overlap between them, there is no rule that forbids having several Schengen visas. Obviously, you would need to pay the fee again, which would be a shame, but at least you might still save your trip.

Advice from the Italian VFS website (probably applies to Switzerland / France also):

(Note - Third paragraph below is the key).

Schengen Visa Information:

A Schengen visa has to be obtained from the Embassy of the country where the MAIN PURPOSE OF TRAVEL lies. Therefore, please check your travel plans before applying at the Italy Visa Application Centre in London.

In case of travel to multiple Schengen countries, please apply to the Embassy of the country where you will be staying for the maximum number of days. If the number of days to be spent in multiple countries is the same, you must apply to the embassy of the country which will be your first point of entry.

Please note that the above rule applies only in the case of a single, consecutive trip to multiple Schengen countries, it does not apply to separate trips to either one or more countries. If you are planning on separate trips to one or more countries, you must apply to the embassy of your first port of entry.

Hope it helps.