New tyre (Falken 452 225/40/18) fitted by mobile fitter. Car driven 2.5m then stood for 20 hrs before noticing that one of the tyres was actually flat.
I inflated the tyre and realised that it had a faulty valve which would hold pressure for only a couple of minutes at the most.
The fitter suggested I mess with the valve myself!

I refused and insisted I have a new tyre & valve fitted at their cost.
Am I within my rights to ask for a new tyre?

I believe damage will have been made to the tyre while being driven/stood flat.