Just to say there are a few of us from Essex or nearby on these boards! Keep your eyes out for some of these names or pm them - they may be able to suggest some schools to try out!
CT (near Wanstead or Woodford I think)
Mark MSP (Harlow)
Njal (Crouch End)
RockChick103 (Near Waltham Abbey)
SarahCol (Near Waltham Abbey)
and me - also near waltham abbey.
Erm as to riding schools there are a few near to me - but I am not sure how far you are able to travel. Havering Park is a bit far away. If travel isn't too bad then let me know I'll rattle off schools and directions. I think the going price for an hour lesson near here is about £20. (Thats why I share - I pay £20 a week and get to ride 4 times for as long as I like!)
Other than that - hope you like the site - Mike and the other moderators are always really helpful and I don't think there is a member on these boards who won't try and help you out if its a horsey issue! We all commiserate, congratulate, rant, rave and praise together on these boards and there is never a question too silly to be asked. Enjoy the site - and happy trails!