Hello. We've just booked our medicals for our 189 visa today and they've attached some information.
This is what ours says (Bridgewater - Manchester):
Permanent Visas
Adult: Medical, HIV and Chest x-ray (£270)
Doctor or dentist: As above, plus Hep B and Hep C (£345)
Child 11-14: Chest x-ray and medical (£190)
Child under 11: £75 (no information given)
Temporary visas
Adult: Medical & Chest x-ray (£240)
Doctor or Dentist: As above (£340)
Child: Medical, Chest x-ray (£190)
Child under 11 (£75)
Prices inclusive of electronic submission or courier fees.
I hope this helps