Personally I always liked the Escort RS over the saffs, bit more gokart feeling. Get a well sorted solid one and it will be a hoot.

Plus, if you get one that isn't pushed to the limits then it wont be as likely to break and if you dont like it, you can sell it on having scratched the itch without seeing much if anything in loss of cash.

I would go S2, S1's are just too much money for a decent one, average S1 money will get you a gem of an S2 or Fiesta RS.