I agree with Steve. However, there is evidence throughout the war, on the various Marks of Spitfire, to show differences in the wheel well colours. Generally, the 'roof' of the well could be the interior colour, 'Cockpit Grey Green', with the 'walls' in the underside colour. When aircraft were re-sprayed, the whole of the wheel wells were sometimes included, and could, for example, end up being the underside colour Medium Sea Grey (on the MkII onwards). For a Mk1 Spit in the BoB era, wheel well walls in 'Sky', and the 'roof' in the grey green would be acceptable as 'representative'.
Photos of the preserved Mk1 in the IWM, when being moved, with the gear down, show the 'green' roof, and walls in the underside colour, and the aircraft of the BBMF have (or had) this finish also.
Again, for the BoB period, the undercarriage door internal faces would normally be the underside colour (Sky), as would the wheels themselves, with the gear legs painted in 'Aluminium', although the wheels could often still be seen in the original 'Aluminium' finish also.