Thanks guys, that's as much as I thought, like I said, it hasn't happened yet and so, it isn't an issue, just thought it was worth investigating!
At the moment the reason I haven't bothered getting checked out on the 172, is that it is more expensive than the 152 for self-fly hire, and I AM ON A VERY TIGHT BUDGET! Having said that, it will make things a lot more flexible, so I will do it soon. I need to log 10hrs this month or else my PPL is dead in the water, so I was looking at this in case of weather/unavailability of 150/152 etc which my restrict access to the planes I am rated/checked out on. Not to worry, but thank you for your input/advice.
Cheers
PM