Kintbury Table Tennis Club uses an online ticketing platform called Eventbrite. Eventbrite allows you to check availability for the Thursday you wish to book. Just enter your name and email address and you're done. Your first session is free and subsequent practice seesions are £4 per person and billed at the end of the month, payment by bank transfer.
It's easy so give it a go!
The Eventbite booking system can be accessed here https://kttc_thursday_practice.eventbrite.co.uk/
You can also install the Eventbrite app on your mobile phone. Search for "Eventbrite" in the app store on your mobile phone.