We'll list a few items / websites / links that may be of use to you.
Driving Test Genie - Driving Test Cancellation Finder
Driving Test Genie - This is a very useful App, which constantly looks for tests and contacts you as soon as an appropriate one becomes available.
This link allows you a free trial, and saves you £3.00 off the normal price should you decide to purchase. The normal price is £17.99, the link will get it you for £14.99
Click the Genie for the discount!