Sign up on line to a credit check with Experian or someone like that.
The check will show your credit status and any applications so you can see if there are any that weren't made by you
The 2 biggest credit reference agencies are eperian and Equifax. You can pay a small amount, and get your full credit reference file from each- you need both as different companies will use each.
If there is something iffy in there, you then write to them and ask them to amend, as well as contacting the company involved.