There are 4 entries for the surname Letting in the Probate Calendar Index between the years 1861 and 1941:
LETTING Thomas Edward of Windmill-cottage Old Bradwell Buckinghamshire died 24 Jun 1924 at the Northampton General Hospital Northampton Administration London 24 July to Amy Rhoda Letting widow. Effects £169 16s. 5d.
LETTING Lucy of Oliver-street Ampthill Bedfordshire (wife of John Letting) died 7 November 1929 Probate London 17 January to the said John Letting retired fish fryer. Effects £845 3s. 8d.
Doris Kathleen of 1 High-street Westoning Bedfordshire (wife of Horace Letting) died 12 April 1936 Administration London 18 July to the said Horace Letting kiln burner. Effects £181 15s. 9d.
LETTING Amy Rhoda of Mill cottage New Bradwell Buckinghamshire (wife of Walter George Letting) died 16 December 1937 Administration Birmingham 2 March to the said Walter George Letting Labourer in railway works. Effect £213 7s. 10d.
There is more information on how you can find index entries outside those years, and how to order Wills or Grants of Administration at the following webpage:http://www.genuki.org.uk/big/eng/Probate.html