I was reading this article yesterday about Andrew Rae the world no.1 O65 fascinating, including the fact that he beat a former grand slam champion Roscoe Tanner, back in 2002. Also interesting that he commutes from Australia to play German seniors team tennis...amazing. 

https://www.itftennis.com/news/292393.aspx

It made me look up the British males in the seniors categories to see who is high up in the rankings:

O35 Dan Cottier WR 12

O40 Luke Milligan WR 10

O45 Sebastian Jackson WR 7

O50 Linden Hardisty WR 16

O55 Nigel Mann WR 44

O60 Paul French WR 7

O65 Jasper Cooper WR 18