The fees are set out in Article 46 and Annex 2 of the Ordinance on Identity Documents for Swiss Nationals (SR 143.116). These are payable in the currency determined by the Swiss representation.

Amount in GBP *
  Identity card Passport 10 Combined offer (passport and ID card Provisional passport (4 or 7 months max.)
Children and adolescents up to the age of 18 31.50 55.50 69.50 80.00
Adults 59.50 119.50 133.50 80.00
Swiss representation's delivery fee local rate local rate local rate local rate

Passport and ID card are posted separately (different places of production). 

All fees must be paid at the time of the appointment. We accept cash, cheques and postal orders (payable to Swiss Embassy), and UK debit and credit cards (Visa and MasterCard).