Entries to the Don days are now via the CA tournament booking system. https://www.croquet.org.uk/?p=members/entry You will need to pay the entry fee at time of booking.
(All Surbiton Members will have been set up as Standard Members of the CA. If you have not logged onto the CA site before then you will need to enter your email (the same one used for the lawn booking system) and then follow the reset password instructions. If you have a query, please talk to any experienced croquet player or contact Don/Max")
For non Surbiton members you will need to contact your own club secretary if your details are not yet on the CA database.