had a local garage change my wheels for winter ones at xmas, they let air out of the summer tyres for me for storage reasons?
I changed them over this week and found the two fronts to be soft, drove about a mile at 20 mph to same garage and asked them to pump em up for me.
They said if i drove at all on the tyres i'd have ruined them and i suspect were tryign to sell me new tyres, I wasnt buying it as my eagle F1s 18's have a good 6-7mm of tread left, the side walls appeared undamaged to me and I persisted in asking them to fillem up since they had let them down. muppets then denied ever letting them down.
They did so begrudgingly and said that they thought the tyres were now dodgy and should be replaced.
have driven them lightly over the past few days and no bother at all, tyres look fine, no bulging of the sidewalls.
My question is should i be worried or were they just trying to sell me some tyres.?

 

Difficult one. How soft were they? If they were soft enough to let the rim grind into the tyre then mechanical damage is likely.

Most of the destruction of a soft tyre is due to overheating and 1 mile at 20 mph is not going to cause this. I once unknowingly drove 50 miles at motorway speed (205/50/16 on a Mondeo) with only 7 psi in a rear tyre, when I had the puncture repaired I inspected the inside walls and they looked OK but I was never really happy with it as damage can be invisible.

Tyre pressures will always fall off with time due to diffusion, at a guess 2 psi per month, you don't notice it in the spring as warmer weather makes the "cold" pressures a little higher.

 

With low pressure comes wall flex. With excessive wall flex at excessive speed comes MASSIVE inner wall wear, plus overheating.
Result: one knackered tyre.