Hi Tony,
Good luck with your challenge.
I started running last January to lose some weight and improve my fitness, but only did my first Park run in the June - coming in at 22:06, followed by 20:50 a few wees later.
I was training to run the Liverpol Marathon in the October, so I gave Parkruns a bit of a miss for a while, but came back to them in November and had by the end of the year had run 20:26, 20:37, 20:15 and then out of nowhere came a 19:51! All of that was really on the back of a long run each week and everything else easy, more about getting used to regular Parkruns. I've had a couple of 19:45s since, but not done a park run for about a month.
I have since done interval sessions each week for 4 weeks and had tempo finishes to my recent longs runs, so I'm hoping for another decent PB in tomorrow's Parkrun.
Hope this proves you can do it Tony, keep working at it!!