Dang i wish i'd caught this thread yday..
The best bet is for sure to walk right up and ask WTF theyre doin..It wont seem dodgy to the cops..like as has already been said, you'd just say ya noticed them for a few days and that being as its close to the holidays,a time when alot of people get burglarized, you thought you'd do the right thing and check it out...
make a note of the Licencse tag, and do a google for unmarked cars in your area... i have found a bunch of cop license tags online.
Its unlikely theyre gonna use a corsa tbh... More likely to be a van or some...
poss even ask a neighbor to use their house as a stake point... but thats real doubtful unless you got real bad odor issues and have a record..
as a rule of thumb, UK cops will just get a warrant and bust ya door out at 4am..
Mre importantly, if the cops do knock your door and provided youve been behaving ya self,and dont got no warrants out on ya etc, they must get a warrant to enter your home..otherwise its unlawful entry.
then you've got at most an hour to get shot of those plants.
just my .2
