I have entered my boy into two local shows coming up next month (eek!) but have not received any confirmation from the organisers.
Do I just turn up on the day or should I have heard anything? I haven't gotten around to checking whether or not the cheques have been cashed yet though, should I take that as my only indication?

Ideally you need to get proof of postage certification when/if you post your show entries.
As this is the only form of proof that the kennel club will accept if the society lose your entry for whatever reason.
For on line entries as long as you get the email confirming your entries from the printers then I think that the KC will accept this as evidence of entries made.

The other thing you can do is pop a stamped address postcard with

"Acknowledgement and acceptance of entries for "xx open show 2010"
in the envelope when you post your entry off.
That way you will know that the secretary has received your entry if it comes back.

You just turn up on the day and hope that your name is in the catalogue!
That's why I always try to get POP (proof of postage) and once it's stamped by the post office I attach it
to the schedule of the show that you've entered and then make sure that  it gets popped in the show bag
on the day of the show. That way if they haven't received your entry they will accept you entering on the day
and then may require you to send it to the KC.

YOu don't get notification unless it's a champ show.

Also many Canine societies don't cash their cheques until near or even after the show,so checking if your cheque has been cashed isn't a true indicator.As said I always get proof of posting from the post office,a free service that takes seconds.