Found it. Isabelle was walking from the direction of Legacy Church in Doncaster. The church has an academy for performing arts but nothing relating to GCSEs from what I can see. The driving test centre is just across the road. I found a School Lane right next to it, it seems to be a new housing estate.
There used to be a place called Kip McGarth on the same road but it seems to have closed down at some point, with the new centre a few minutes drive down the road. Kip McGrath do tutoring but I was unable to fid out if you can sit GCSEs there. I wouldn't put it past them to drive to a random place, film Isabelle go in and pretend she's doing the exam before filming her walk back.
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