If you are on Facebook, have a look at the Speedway Friends Group. Karl Fiala has posted hundreds of "Where are they now?" posts where ex riders answer the type of questions you are asking.
Are you a member of the Speedway Scrapbook Facebook Group? If so, there is a Swedish guy called Omar Nilsson who lives in Sweden and posts old photos regularly. He may be able to help you find this information if it's available in any Swedish Speedway archives.
There's a Ron Dirkin listed in the Speedway Riders Index 1929-2022 with no career record details. No mention of a Roy Dirkin.
There is also the caveat that the Index document contains "Rider careers are for League and KOC/National Trophy matches only. "
Taken from the Speedway Riders Index 1929-2022
DeWayne KEETER Born: 15 October 1944, Ventura, California, USA. Died: 2 May 1975 - following a track crash at Ascot Park, USA. Career record: (1969) Leicester. International honours: USA international (2 caps).
1981 World Final at Wembley - Apart from the two Bruce Penhall races, it's the only meeting I've ever been to where you couldn't hear the noise from the bikes due to the noise that the crowd was making. What an atmosphere.