I've got the following but data may be a bit out of date, last updated 2012. The actual data was compiled by someone else some time ago but I cannot remember who, I think it was from a website or forum (perhaps even here?).
https://www.dropbox.com/s/u93lgtlm4nkt542/StandardTimes%20Amended%20graphs.xls?dl=0I've taken the data for GB and IRE and separated by Flat, Chase and Hurdle. I've then plotted time(s) vs distance (furlongs) and just taken linear best fit which is fairly accurate. It gives 3 formula to calculate race time based on number of furlongs
Flat: Time(s) = 14.057 * furlongs - 13.908
Chase: Time(s) = 15.394 * furlongs - 16.574
Hurdle: Time(s) = 14.549 * furlongs - 10.663
Obviously there is more variance the longer the race is based on other factors such as class, going and other racing conditions.
I can't see this being too far adrift now that it's 2019.
Os