The pair of you are like the 2 Ronnies
Her mum has an almost empty double garage in Bearsden that I use on rare occasions, I'm not sure how she'll feel about a stranger being in there fiddling with gubbins though.
If it was something like an interior swap that could be done in a day (or a few days - just leave the car in there) I'm sure she'd be fine with you using it aslong as I'm there aswell, my old mum lives 5 minutes from there so it's not too big a deal.
She always has an endless supply of chocolte biscuits aswell
