Ian,
I decide to make a 180 and return home
I'm probably teaching grandma to suck eggs, but don't forget that to return to base will probably not require a simple 180 heading change, but you should treat it as any in-flight diversion and allow for wind direction & speed.
I had to return to base on the first and second attempts at my QXC due to low cloud draping itself across the mountains of mid-Wales. The most difficult part was in actually making the decision to abort as there is a certain amount of expectation and thus added pressure that you will go from A>B>C>A as planned. The fact that you are considering the possibility in advance means that you shouldn't be too fazed by it.
Good luck and enjoy it.
Mr. W