I’m completely confused. Grizedale and Whinlatter are a long way away and riding between them in a day will be mainly tarmac. Driving between them in a day is a day in the car with hardly any biking in between. Especially if you are coming from Chorley first and want to get back there at night. That’s a mad, daft plan.
Drive up and park somewhere in the south lakes. The north lakes from Chorley is a bit of a trek. You can get maps from Biketreks, Wheelbase or if you must do a set way marked trail then go to Grizedale.
If you chose to ride TNF trail, you can do additional exploring of bridleways without a map as you can always easily pick up one of the family routes or the road and they are all signposted to the visitors centre.
You don’t need to know the area. Before trail centres, people used to purchase OS maps and just follow the bridleways. It’s even easier now they’re all signposted clearly. You don’t even need a map in some areas, just a sense of direction.