One wheel on my wagon ...... seems to have a flat

When we moved here we were newly retired. We picked this house because it was just around the corner from the railway station and a nice level walk / bicycle ride into town. Previously we were both working and heading off in different directions each morning so we moved here with two cars and barely enough use for one of them. We're loathe to sell one (neither would fetch a lot) as it does give us flexibility so it tends to be that MrsW's little Micra barely gets used. This morning she decided to take it into town to do some shopping and give it a run. When she got back she says to me "I'm going to need some more air in one of the tyres". MrsW is no mechanic, and although I spent many a year driving a 3.5 ton book van around educational establishments between Aberystwyth and Brighton neither am I. However I have learnt along the way how to inflate the tyres with air which I am afraid MrsW has not. I stand corrected here. She says she has learnt but she doesn't like the hissy thing. "Ok" I say "I'll take it up to the garage for you and put some air in". Except when I get outside I immediately decide against this option. As the man says "It was only flat at the bottom of the tyre" but it was very flat. "I'm sure it's lost more air since I left the supermarket" says MrsW. So the car sits on the drive until Monday when I will attempt to fit the odd looking little spare wheel and set off to get a new tyre.