Wing filler caps on Spitfire PR I (C & E types)

[Spitfire pr1v]

Hi All

I know this is a long shot given the lack of technical information on early PR I Spitfires.
At present modelling a Spitfire PR IC and wondered if anyone knows were the filler cap for the wing tank ( PR IC or PR IF ) is located ?
Behind the small blister on the wing maybe, which I believe covers the tank fuel pump ?

Thanks