@pipion – yes Surrey Hills and stay South/South West so you can access the A3. I live in SW3 and can get to Surrey Hills in just under an hour on a Saturday/Sunday morning leaving around 8:00, traffic is pretty light. More trouble if you try and get back into London on a Sunday at 5pm
In terms of where to head for I would drive to Peaslake and/or hook up with Nirvana in Westcott for a shop ride perhaps ? FWIW Dorking wouldn’t be where I would start from. If you want an XC+ style ride you can park at Newlands Corner (large car park, cafe etc) and ride along the NDW towards Ranmore (few trails/features there 🙂 ) then come back on South side through Shere. That’s about 20 mins less driving than Peaslake. If you want a map/suggestions drop men an email