Cyclocross - CX and SSCX races and training

The Heath Extension https://goo.gl/maps/8RcG3o6hE222 has some nice bits, if you enter from Spaniards End those routes are quite easy to find.

https://goo.gl/maps/GYRZsyvdzPn
This bit of green is also good and a bit closer to town (entrance off priory gardens) however there are a fair few rough sleepers in that park, so be careful you're not doing laps of someone's tent or they might get a bit brassed off (yes, I speak from experience).

I have no idea if you're allowed to cycle on those bits so be considerate to others obvs and don't blame me if dog walkers shout at you.

These are also good urban cx routes if you want a longer ride

https://ridewithgps.com/routes/18354797

or

https://ridewithgps.com/routes/18374870

but easy to get lost on, so again, don't blame me