I would also point out you have taken it to a Subaru specialist And Subaru clinic has a reputable name in the industry, not sure they will want to get involved mind but a bit of names dropping won't hurt to the garage you bought it from and point out they have said this is the problem. if they refuse to sort it after
Now I know we had a post about Tony Hough I don't have his details but I've taken note and he does seem to have some good feedback for being cheap and doing a good job. so i can source that for you in Rotherham. I would recommend Martin every day of the week but I am a fan of the underdog and martin has never let me down, so I'd also recommend him. Unless you want Clinc to sort it that is your choice I have nothing against them personally. But least you have alternative options if the garage you bought it from refuse to sort the issue. You might need to pay for the repair then court to get cash back.
I'd only worry though if it was what the garage said it was in part x sold as seen. In other words it was quickly looked at an taken in nothing done to it and sold on as quick as they took it in. I'd also message Alex he has an ongoing battle with a garage for his car. :)