You might want to try
ABetterRoutePlanner back to your destination ... perhaps experiment with 20%, 30% ... as the START charge, and see where it recommends you charge. Planning to NOT charge at West Drayton might be best, more likely that will be full than if there are alternatives available on your route.
Reading (M4), Oxford (M40) and South Mimms (M25/A1) are "not far" ... M1 is more tricky and for anything M25-South I'd use Heathrow if West Drayton busy
In case you aren't already aware:
On SatNav the Bright Red Pins for Superchargers are "within range", just click and press [Navigate]. The light-red pins are "out of range". If you click on a Supercharger Pin it will tell you the number of stalls free - that will change before you get there, but might help you decide between e.g. West Drayton and Heathrow
If you "pair" you will have significantly less power, until the other car leaves or gets to high enough %age that it tapers. So best to avoid (Stall Pairs are labelled A/B, usually next to each other but not always)
I had a go at a Model-3 Collection FAQ, the following posts also have useful info
What New Owners need to Know - UK FAQ
Enjoy you new car