It looks like going through the Blackwall Tunnel and straight out on the A20 will be the easiest option from Canary Wharf - it's 19 miles to Brands.
If you want to head over this way and meet after work just let me know. There's a McDonalds at the Canary Wharf junction of the A13 so can meet in there and grab something to eat before heading out if you want.
Route here:
https://maps.google.co.uk/maps?saddr=McDonald's+Trafalgar+Way,+McDonald's+Tr afalgar+Way,+2+Trafalgar+Way,+London+E14+5SP,+Unit ed+Kingdom&daddr=Thistle%E2%84%A2+Brands+Hatch+hot el,+Dartford&hl=en&ie=UTF8&ll=51.435604,0.121536&s pn=0.290645,0.42778&sll=51.504469,0.066605&sspn=0. 290207,0.42778&geocode=FXPvEQMdR9z__ynzvlmrrwJ2SDG 9m_tkz3TiVg%3BFaCsDwMdJN4DACHMRoGUUZc4kCnbi3eTObPY RzHMRoGUUZc4kA&oq=mcdonalds,+cana&t=h&mra=pd&z=11