The good news ;-

If you wait to apply till after you are married the visa fee is free.



The following categories do not have to pay the visa application fee:
  • Short stay for children under six years of age
  • Short stay private visit for groups of scholars participating in a school exchange program or in training courses
  • Invitation by some international organization whose headquarters are based in France
  • French citizen's spouse
  • EU citizen's spouse
  • EU citizen's child under 21 years old or dependent
  • Ascendant dependent of EU citizen
  • Short stay for scientific researchers/students traveling for scientific research
  • French teachers currently teaching
  • Holder of a governmental scholarship for study
The bad news ;-

http://www.ambafrance-uk.org/Latest-news,17918.html

As per 15 September
In order to improve the standard of service to the visas applicants, the French authorities have decided to outsource the information of visa applicants and the collection of visas application to the company TLScontact. This service is available regardless of the nationality, the type of passport, the duration and the purpose of the stay of the visa applicant.
The service fee, mandatory for any visa application, is GBP 23,33 .

https://www.tlscontact.com/gb2fr/login.php

This outsourcing only seems to apply for England and Wales. Residents in Scotland and IOM can still apply at the consulate in Edinburgh.