I wonder if Bill gave Colin permission to go blabbing to the media? I am very glad he did, it is one more version of his day locked in for the police to compare to his statements, which were apparently a bit loosey goosey to start with. I'm another one with zero access to time of transaction on my statement, I'd assume that's info you can only get from the bank, if you even can. I'm gonna guess this is something he has said to Colin to bolster his alibi to his mate and this will hopefully bite him in the bottom also.
The "surprise" visit thing has caused some confusion. His grandmother was expecting them to arrive Friday, but they arrived the night before, William's parents cleared that up in their interview. If I had to make a bet, it'd be that Bill Spedding knew she was expecting guests but the abduction was on the spur of the moment. Maybe it was just enough extra info to know William's name to get him closer. Maybe William was just enough confused about his passed grandfather than he was a little more trusting of this stranger than his parents characterised he would be. I can imagine a 3 year old, who has just been drawing for his grandfather and being spoken to about him, who doesn't have a full grasp of what dead means, and knows he's going to go "see" him soon, is at the house for the first time without grandad there, could be confused enough about what eldery man it actually was.