What is the best option to repair a twisted chain?
What do you mean by "twisted"? Are there any links that are bent? Or are there simply stiff links caused by gunk, rust, neglect?
Most probably you will need to replace the chain. That will set you back about 15 (12 GBP / 20 USD / 23 CHF), depending on what type of chain you need and where you buy it. If the chain is quite new, you could just replace the damadged links (you kept the links you did not need when you replaced the chain, did you?).