Wheel, petrol guage and lights

The Daimler is running well.  But running an old car means that there is always something to sort, or in this case 3 things to sort.  I finally bought a spare wire wheel - since converting to wires I have not had a spare.  Does anyone know the best source of cheap tyres for these cars?  I do not need a good quality tyre - just a spare that works, and will hold air.

Today I took the car to a local supermarket - glancing at the fuel guage gave me a fright as it was showing empty.  When I popped it in the garage a couple of weeks ago it was showing a quarter.  I hoped it was the guage and not a leak.  I filled it at a local garage - about 7 miles away, still no movement on the guage.  Ideas anyone?

The third thing was the cover from the interior light fell off whilst I was driving.  I will have to have a look at how it is supposed to be held on - it would appear that it has been held on by blu-tack, which I suspect is not how Daimler used to build them