Hi Andy,
Yes, you are correct. Fuel pumps do show in litres and petrol is priced using pounds per litre.
The 'gallons' thing is one of many hangovers we have here in the UK becuase we have never fully put into action any policy to adopt metrication. We are SUPPOSED to - but in reality either never have or have only done so on a very half hearted basis!
I like your example concerning the South West of the USA. I seem to remember that in some parts of the Republic of Ireland there might be (or have been) a similar situation with distances in one unit and speed limits in another. Robbie will know the answer to this
Regards