At Wadhurst you are some distance from the Surrey sites - perhaps the best part of an hour's drive. But you are within minutes of Sussex's only accessible iron mine (all mines bar this one were just pits sunk to the ironstone with no side galleries). However, the mine is on forestry land, and access is only possible via Kent Underground Research Group, who though willing, will require notice of the visit and probably need to inform the forestry people. You can see all the site easily in less than an hour. (Snape Wood - see the mines index). Let me know if you are interested and I will give you a contact. You might be better off leaving any Surrey visits until you are in London, though it does depend on where you are going to be based as to how easy it is to get out of town. If you are into industrial history, and have the time, try to visit the Kew Bridge Steam Museum to see the largest collection of working Cornish engines in Britain, the Science Museum to see a number of very early engines - atmospheric, Watt, and a Trevithick machine, and the famous Rocket locomotive (it's free as well). There's plenty more to see of course, but you have to leave some hours for the usual rubbish like Buck House, HofP, Westminster Abbey bla bla bla. 🙂