Sussed it, set the "Simple Track" setting to OFF and everything is back to normal.

Quote from shim :

in Q did you change any of your gpx settings? cause with the new patch, everything is put back to stock pretty much..

Always used to run with default settings. Have had a play and turn off almost everything and still the FR is poor....very odd

Yup I am experiencing the same, frame rate has dropped to low 20's at the starts and doesn't go over 45 now. Used to be twice that