It was at the farm on the day of the murders. Bamber probably put it somewhere out of the way.
So if it was at the Farm on the day of the murders, and Bamber hid it somewhere how did he get back to his house? Julie say's the Bike wasn't at the house on the 7th so it must have been at the Farm and say's she never saw it again, ann never seen it till the 22nd of August at Bambers outside the back door.
Could well be he bought the cycle back on the 4th of August for a trial run along the sea wall and he thought "fook that for a game of soldiers"

When do you plan to Power Cycle along the Sea Wall LANCE on your Ladies Cycle in the middle of the Night, i would Personally pay to watch you do it, as i'm sure others on here would.