In March 2019, Jonny’s ashes were interred at Golders Green Crematorium in the memorial gardens.
Visiting the memorial
The address is 62 Hoop Ln, London NW11 7NL.
Crematorium website: https://www.thelondoncremation.co.uk/golders-green-crematorium/
Crematorium phone: 020 8455 2374
As you enter the memorial gardens, the memorial is towards the left-hand side of the grounds. It is near the sculpture called Into The Silent Land by Henry Alfred Pegram:
The white stone near the bottom of the photo is Jonny’s. 
A view down the path towards the entrance/exit.
The following map shows the location of the memorial in the grounds:
The Memorial Gardens are open 365 days a year.
April – September 9.00am – 6.00pm
October – March 9.00am – 4.00pm