VAT Query - Self Supply

If a business carries on the trade of a motor dealership and a petrol station, would the company be entitled to reclaim the VAT on the cost of filling a car purchased in the dealership with Diesel/Petrol used from the filling station. I think this may come under Self supply rules but am having difficulty finding anything specific on it.

Example, Company A reclaims VAT on a petrol/diesel delivery used to fill the pumps in the filling station. Mr X. purchases a car from Company A through the motor dealership and as a goodwill gesture Company A fills the new car with petrol/diesel. It is recorded through the till on account (otherwise petrol machine in shop would have outstanding transaction on it and would continue to beep) and is picked up in the VAT on Sales. Should Company A then record an additional VAT on Purchase for the petrol/diesel to cancel the VAT on sale above? Overall, the net of the above transactions is that company A gets a VAT input.

Apoligies if the above is confusing but can't think of a better way to explain it...