For the loss of the Liberal Democrat majority on Guildford Borough Council during 1997 see
a) 2 Liberal Democrat councillors for Stoughton quit the party to be Independent Liberals in February 1997 reducing the number of LD councillors from 23 to 21: http://www.getsurrey.co.uk/news/s/80053_leading_lib_dem_couple_quit_party
b) Liberal Democrats lose Merrow & Burpham by-election to Conservatives in May 1997 reducing number of LD councillors from 21 to 20. Fuller details of this by-election are listed at [Guildford local elections]; and
c) 1 Liberal Democrat councillor for Tongham quit the party to join the Put Ash Vale First Group (which was then renamed the Independent Group) in May 1997 reducing the number of LD councillors from 20 to 19. See: http://www.getsurrey.co.uk/news/s/80321_borough_chaos_as_councillor_defects .
At the time 23 seats were needed for a majority.