Hi Guys I just finished the thieves guild in Oblivion (360) so I have a few tips for you for the 2 last missions The Spring heel jak and the ultimate heist-
1.In the spring heel jak one go to his house by asking the beggars then in his house go upstairs in the private quarters and find a man named Jakaben-earl of-Imbel or something like that kill him and search his body and you will have the boots of springheel jak there grab them and take them to gray fox.
2.In the ultimate heist when you have got the elder scroll and you don’t have or want the stolen goods you have then you can just can go downstairs and activate the way you came from a quest update message would appear that you have escaped but actually you are still in the castle then talk to any guard in the castle and select go to jail. This way you can escape easily from the imperial castle and have the boots of springheel jak also.